Chapter LVI: Appendix: G (1)

THE INHERITANCE OF FUNCTIONALLY-CAUSED MODIFICATIONS.

In Part II, Chapter X^A, I have confessed that the process by which a structure changed by use or disuse affects the sperm-cells or germ-cells whence arise descendants, is unimaginable: without, however, inferring that therefore such a process does not exist. With others it seems different. Some three years ago the following expression of opinion came to me from a zoological expert:--

“Many zoologists--most of us here at Cambridge--are intensely
opposed to the doctrine of the inheritability of acquired
variations. Even assuming that the developmental power of a
germ is determined by its molecular structure (and I for one
would question this--Driesch and his school when they find that
they can squeeze a developing egg into all sorts of shapes
without altering the final result, that one blastomere in an
egg which has divided into 8 is still able to reproduce a whole
embryo--question it also), we still fail to conceive any means
by which, for instance, a change in the development of a muscle
or nerve can effect a corresponding change in that part of the
germ which is destined to produce a corresponding part in the
descendant.”

Here it will be observed that belief in the inheritance of structural effects wrought by use and disuse, is rejected because of inability “to conceive any means” by which the modifications produced in an organ can effect a correlated modification in the germ of a descendant: failure to conceive is the test. The implication is that some alternative hypothesis is accepted because the correlating of a variation in an organ with a corresponding germ-variation is effected by a means which _is_ conceivable. This is the hypothesis of Weismann. Concerning its conceivability I have, in the chapter just named, already written as follows:--

“If we follow Prof. Weismann we are led into an astounding
supposition. He admits that every variable part must have a
special determinant, and that this results in the assumption of
over two hundred thousand for the four wings of a butterfly.
Let us ask what must happen in the case of a peacock’s feather.
On looking at the eye near its end, we see that the minute
processes on the edge of each lateral thread must have been in
some way exactly adjusted, in colour and position, so as to fall
into line with the processes on adjacent threads: otherwise the
symmetrical arrangement of coloured rings would be impossible.
Each of these processes, then, being an independent variable,
must have had its particular determinant. Now there are about
300 threads on the shaft of a large feather, and each of them
bears on the average 1,600 processes, making for the whole
feather 480,000 of these processes. For one feather alone there
must have been 480,000 determinants, and for the whole tail
many millions. And these, along with the determinants for the
detailed parts of all the other feathers, and for the variable
components of all organs forming the body at large, must have
been contained in the microscopic head of a spermatozoon!” [And
each of them must, throughout all the complex developmental
processes, have preserved the ability to find its way to the
exact place where it was wanted!]

If my Cambridge correspondent is able to conceive this process implied by the hypothesis of Weismann, I can only say that he has an enviable power of imagination.

* * * * *

But now comes the strange fact that an impossibility of thought implied by Weismann’s hypothesis does not cause rejection of it, but yet is urged as a reason for rejecting an alternative hypothesis which does not imply it. One objector cannot conceive that “a change in the development of a muscle or nerve can effect a corresponding change in that part of the germ which is destined to _produce a corresponding part_ in the descendant”; and another objector says it is “very hard to believe” that a functionally-changed organ will so affect spermatozoa and ova that “_one particular part of them_ will be so altered that the organisms which grow up from them will be able to present the same modification on the application of a different stimulus.” It is tacitly assumed by both that, as in the hypothesis of Weismann so in the counter-hypothesis, a particular part of the germ-plasm gives origin to a particular part of the developed organism. But nothing of the kind is implied. The nature of the counter-hypothesis (at any rate as held by me) is entirely misapprehended. Anyone who turns back to the chapters in the first volume where the conception of physiological units (or constitutional units) was set forth, or who re-reads the foregoing appendix, will see that there is altogether excluded any idea of correlation between certain parts of the germ and certain parts of the resulting organism. The units are supposed to be all alike, and during the progressive embryological changes local groups of them are supposed to take on different forms and structures under the combined forces, general and local, brought to bear on them. This conception is necessitated by all the evidence. The fact disclosed by the experiments of Driesch, Wilson, and Chabry, that from fractions of an ovum structures may be obtained like that obtained from the whole ovum, only smaller, necessitates it. The fact that any sufficiently large fragment of a polyp or planarian, no matter from what part of the body taken, will develop into a complete polyp or planarian necessitates it. The fact that from an undifferentiated portion of a plant, even so small as a scale, a complete plant may arise necessitates it. And it is necessitated by the fact that among plants, roots are produced by imbedded shoots and shoots by roots, as well as by the fact that low animals, such as hydroids, if deprived of both head and root, will develop a head from the root part and a root from the head part, if their respective conditions are inverted. All this evidence shows conclusively that the component units of each species, whether existing in the germ or in the developed organism, are, when not yet differentiated by local conditions, all alike, and that the notion of special parts of the germ-plasm correlated with special parts of the resulting organism, is entirely alien to the hypothesis.

“But how do the units of a modified organ affect the units of the germ in such wise that these produce an inherited modification of the organ?” will be asked. This difficulty has been dealt with in §§ 97_d_, 97_e_, where the analogy between the social organism and the individual organism has been brought in aid: serving, if not to furnish a conception, yet to furnish an adumbration. Regarding citizens as the units of an unfolding society, say a colony, it was pointed out that the nature they inherit from a mother-society gives them a proclivity towards a society of like structure, the traits of which are progressively assumed as the colony grows sufficiently large to make them possible. At the same time it was pointed out that while the influence of the entire aggregate on the individuals is seen in this forming of them into a society of the inherited type, the influences of local circumstances, and of individuals on one another, in each group, make them differentiate into appropriate social structures, taking on fit occupations and industries: the implication being that in virtue of their inherited natures they all have partial capacities for the various activities they undertake; so that an immigrant clerk sets up a tavern, a compositor takes to carpentering, and a university man rides after cattle or is employed on a sheep farm. Evidence was given in that place, as in the above paragraph, that the constitutional units of an organism similarly have all of them potentialities for taking on this or that structure and mode of action which local conditions determine. It was further argued that as citizens are continually being remoulded by their society into congruity with it, and, if circumstances change them, tend to remould their society; so in the individual organism, there is this reciprocal action of the whole on the units and of the units on the whole. Hence it was inferred that the modified units in any modified part tend to diffuse modifications like their own through the units at large: being aided by the circulation of protoplasm, as suggested in §§ 54_d_ and 97_f_. And it was urged that, however inconceivably complex such a process may be, yet it seems not incredible when we recognise the probability that an organism is more or less permeable to undulations propagated by its molecules: Rontgen rays giving warrant. If such units throughout the tissues may take in and send out ethereal waves which bring it into rhythmical relations with others of its kind and tend to produce congruity, it becomes, if not conceivable still supposable, that throughout the circulating protoplasm there goes on a continual harmonization of its components--a moulding of each by all and of all by each. Should it be said that such a process is too marvellous to be reasonably assumed, the reply is that it is not more marvellous than heredity itself, which, were it not familiar to us, would be thought incredible.

* * * * *

But as I have said in the place referred to--“At last then we are obliged to admit that the actual organizing process transcends conception. It is not enough to say that we cannot know it; we must say that we cannot even conceive it:” can only conceive the possibility of a suggested interpretation.

Hence we have to rely upon evidences of other kinds. Among these, some which I think dispose absolutely of the fashionable hypothesis while they harmonize with the opposed hypothesis, have now to be named. That their implication should not have been generally recognized would have seemed to me incomprehensible were it not that I have myself only now observed this implication. The facts are these:--

“Verlot mentions a gardener who could distinguish 150 kinds
of camellia, when not in flower; and it has been positively
asserted that the famous old Dutch florist Voorhelm, who
kept above 1,200 varieties of the hyacinth, was hardly ever
deceived in knowing each variety by the bulb alone. Hence we
must conclude that the bulbs of the hyacinth and the branches
and leaves of the camellia, though appearing to an unpractised
eye absolutely undistinguishable, yet really differ.” (Darwin,
_Variation of Animals and Plants, &c._, vol. ii, p. 251.)

More recently testimony to like effect has been given by Dr. Maxwell Masters, and has already been quoted by me in a note to § 286 in illustration of another truth. He says concerning such variations:--

“To the untrained eye, the primordial differences noted are
often very slight; even the botanist, unless his attention
be specially directed to the matter, fails to see minute
differences which are perceptible enough to the raiser or his
workmen.... These apparently trifling morphological differences
are often associated with physiological variations which render
some varieties, say of wheat, much better enabled to resist
mildew and disease generally than others. Some, again, prove to
be better adapted for certain soils or for some climates than
others; some are less liable to injury from predatory birds than
others, and so on.”

In his _Vegetable Teratology_, p. 493, Dr. Masters names another fact having a like implication--the fact that among seedling stocks which have not yet flowered, those which will produce double flowers are distinguishable. He says:--

“This separation of the single from the double-flowered plants,
M. Chatié tells us is not so difficult as might be supposed. The
single stocks, he explains, have deep green leaves (glabrous in
certain species), rounded at the top, the heart being in the
form of a shuttlecock, and the plant stout and thick-set in its
general aspect, while the plants yielding double flowers have
very long leaves of a light green colour, hairy and curled at
the edges, the heart consisting of whitish leaves, curved so
that they enclose it completely.”

What is the general truth implied? Clearly that there exists no such thing as an independent local variation. Some marked change in the form or colour of a flower or a fruit draws attention; and, being a change which interests the florist or gardener, pecuniarily or otherwise, not only draws attention but usually monopolizes attention: the natural impression produced being that this variation stands there by itself--is without relation to variations elsewhere. But now it turns out that there are concomitant variations all over the plant. Even in underground bulbs certain appreciable differences go along with certain conspicuous differences in the flowers. And if along with a striking change in a flower which the florist contemplates, there go changes all over the plant not obvious to careless observers but visible to him, we must infer that there are everywhere minute differences which even the florist cannot perceive: the whole constitution of the plant has diverged in some measure from the constitutions of kindred plants. Every local variation implies a change pervading the entire organism, manifested in concomitant variations everywhere else.

If so, what becomes of the hypothesis of determinants--the hypothesis that there is a special element in the germ-plasm which results in a special local modification in the adult organism? That there are no facts supporting it has been all along manifest; but now it is manifest that the facts directly contradict it.

At the same time it may be remarked that while the facts are wholly incongruous with the hypothesis of determinants and its accompanying elaborate speculation, they are not incongruous with the alternative hypothesis. Impossible though it may be to imagine the natures of those ultimate units peculiar to each species, which have proclivities towards the particular form of organization characterizing it, yet that a change of structure arising in one part of the organism is accompanied by multitudinous changes of structure in other parts of the organism, is not only congruous with the belief that there exist such constitutional units, but yields it distinct support. For if, as above argued, a conspicuous local variation is not the result of any modification of units special to the locality, but is the result of a modification of the units at large, then it must happen that such modification must have its effects on all other parts of the organism; so that there cannot fail to result all those small concomitant variations above indicated.

May we not also say that it becomes less incomprehensible that structural changes caused by use and disuse are inherited? If, as we see, a local variation spontaneously arising is accompanied by multitudinous other local variations, implying a necessary correlation between each local variation and the general constitution of the organism; then it may be argued that if a marked change of function in an organ causes increase or decrease of it, this general correlation implies that there must be a reciprocal reaction between the part and the whole, tending to re-establish their congruity. The constitution at large will in so far be changed, and along with its change will go corresponding changes in the sperm-cells and germ-cells.

* * * * *

Finally let me add, not another argument, but another fact of observation, of the kind which opponents demand, but which, when they are from time to time furnished, are severally pooh-poohed as not enough. Each of them is spoken of as a solitary fact and slighted as inadequate; and when by and by another is named, this is treated in the same way; so that the facts which if brought together would be recognized as sufficient are never brought together. That to which I refer is set forth in a pamphlet by M. Leo Errera, Professor at the University of Brussels, entitled “Hérédite d’un Caractère acquis chez un Champignon pluricellulaire;” being an account of experiments of Dr. Hunger, at the Botanical Institute in Brussels. First enumerating various instances of adaptations to climate, as those of plants which, fitted to northern regions, preserve their constitutional rapidity of growth and seeding when brought south, and do this for several generations, he goes on to detail the culture-experiments of M. Hunger, and sums up the results of these in the following words:--

“On déduit de là que:

“1^o Les conidies d’_Aspergillus niger_ sont adaptées à la
concentration du milieu où a vécu l’individu qui les porte; cet
effet est encore plus marqué après deux générations passées dans
un milieu donné (Expér. I et II);

“2^o II s’agit d’une véritable adaptation et non pas simplement
d’un accroissement de vigueur chez les conidies provenant des
liquides concentrés, car ces mêmes conidies germent moins
rapidement et donnent des plantes moins vigoureuses que
les conidies normales lorsqu’on les sème de nouveau sur le
milieu-type: en s’adaptant aux liquides concentrés, elles se
sont _désadaptées_ du liquide normal (Expér. III);

“3^o Une génération passée sur le liquide normal n’efface pas
l’influence d’une ou de deux générations antérieures passées sur
une liquide plus concentré (Expér. IV).

“Tous ces résultats concordent: _ils montrent une légère, mais
incontestable transmission héréditaire de l’adaptation au
milieu_.”

SUBJECT-INDEX.

(For this Index as it appeared in previous editions the
Author is indebted to F. HOWARD COLLINS, Esq., of Edgbaston,
Birmingham. It has now been adjusted to suit the present revised
and enlarged edition.)

Acacia, foliar organs, =II=, 41, 264.

_Acalephæ_: environment, =I=, 105;
water in, =I=, 173.

_Acari_: special creation and effects of, =I=, 428;
direct transformations, =I=, 706;
segmentation, =II=, 111.

_Acorus calamus_, agamic propagation, =I=, 642.

Acquired characters, inheritance of: functionally-produced
modifications in plants and animals, =I=, 307–13, 318, 526,
541, 562, 692–5; =II=, 618–22;
conceivability of, on the hypothesis of physiological units, =I=,
368–71, 695; =II=, 618–22;
diminution of jaw, =I=, 541–2, 693;
current views on, =I=, 559–60;
cessation of selection, =I=, 560–3;
Eimer’s theory of orthogenesis, =I=, 560;
species differentiation, =I=, 573;
location of mammalian testes, =I=, 573;
tactual perceptiveness, =I=, 602–8, 633, 665, 666, 672–3, 692;
blindness of cave-animals, =I=, 612–3, 647–9;
co-adaptation of co-operative parts, =I=, 621, 663–5;
transmission of disease, =I=, 622–3;
hypothesis supported by telegony, =I=, 624–8, 644–6, 649–50;
views of Darwin and neo-Darwinists, =I=, 630, 685, 690;
why facts in support are meagre, =I=, 632;
degradation of little toe, =I=, 652–3, 673;
neuter forms of social insects, =I=, 658–9, 663–4, 670, 675;
degenerated instinct in ants, =I=, 660–2;
rudimentary limbs of whale, =I=, 669, 692;
importance of question, =I=, 672, 690;
monstrous development of honey-ants, =I=, 683–4;
osteology of Punjabis, =I=, 689;
summary of evidences in support, =I=, 692–5;
genesis of vertebrate skull, =II=, 227;
false joints, =II=, 371, 372;
conceivability of rival hypotheses, =II=, 618–22;
adaptation to environment in _Aspergillus_, =II=, 623.

Acrogens, the term, =II=, 55–6.
(See _Archegoniateæ_.)

_Actinophrys_: a primary aggregate, =II=, 76;
genesis, =II=, 452.

_Actinozoa_: multiaxial development, =I=, 166;
waste and repair, =I=, 213, 219;
differentiation, =I=, 391;
parasitism, =I=, 397;
integration, =II=, 92;
symmetry, =II=, 189, 192;
growth and genesis, =II=, 444.

Activity: the principle of, the essential element in Life, =I=,
113, 114, 122;
not inherent in living matter, =I=, 120;
nutrition and genesis, _résumé_, =II=, 497–9;
and evolution, =II=, 501–4.

Adaptation: general truths, =I=, 227–33, 233–5;
botanical, =I=, 227;
physiological, =I=, 228–33;
psychological, =I=, 229, 230–3;
structural, functional, and interdependence, =I=, 235–9, 240–1,
318;
social and organic stability, =I=, 240–2;
_résumé_, =I=, 242–3;
to varied media, =I=, 479–81, 489, 556;
multiplication of effects, =I=, 512–3, 550;
direct equilibration, =I=, 522–3;
natural selection and equilibration, =I=, 530–5;
non-adaptive specific characters, =I=, 565;
time required for effecting, =I=, 565–6;
an obstacle to re-adaptation, =II=, 11;
of skin and skeleton, =II=, 215, 217;
outer tissue, =II=, 312–4, 387;
skin and mucous membrane differentiation, =II=, 321–2, 389;
vascular system, =II=, 343–4;
osseous, =II=, 352;
muscular, =II=, 368–9, 391;
persistence of force and physiological, =II=, 394;
of reproductive activity to conditions, =II=, 411–6;
vertebræ development, =II=, 563–6.
(_See also_ Co-adaptation.)

Africa, effect of climate on inhabitants, =I=, 30.

Agamogenesis: alternation with gamogenesis, =I=, 266–7, 272–3,
284–94, 336, 592; =II=, 415;
parallelism in karyokinesis, =I=, 267–8;
a process of disintegration, =I=, 276–7;
conditions determining its continuance, =I=, 284–94, 295–7, 330;
physiological units, =I=, 351; =II=, 613;
spontaneous fission, =I=, 582, 584–7, 589–92, 595–6, 599;
remarkable extent of, under favourable conditions, =I=, 591–2,
640–1;
in _Actinozoa_, =II=, 92;
in _Hydrozoa_, =II=, 102;
in _Annelida_, =II=, 103;
innutrition, =II=, 179–80.

_Agaricinæ_, =II=, 139, 257.

Agassiz, L. J. R., zoological classification, =I=, 380.

Aggregates, Animal and Plant (_see_ Morphology).

Agility, a vital attribute, =I=, 578.

Agrimony, floral symmetry, =II=, 42, 167, 170.

Air, in vegetal tissues, =II=, 567–8, 583, 591, 593.

“Air plants,” =I=, 208.

Albumen: properties, =I=, 12;
Lieberkühn’s formula, =I=, 13;
diffusibility, =I=, 19;
in organic tissues, =I=, 41.

Alcohols, properties, =I=, 10–12.

_Algæ_: reproduction, and the dynamic element in life, =I=, 118–9;
multicentral development, =I=, 163, 164;
axial development, =I=, 165;
locomotive powers of minute forms, =I=, 196;
uniform tissue and function, =I=, 200, 586;
gamogenesis, =I=, 271, 279, 280, 283; =II=, 448, 449, 450;
fertility, =I=, 582; =II=, 440, 441;
fission, =I=, 584, 585;
unicellular forms, =II=, 22;
integration in _Confervoideæ_ and _Conjugateæ_, =II=, 25;
pseudo-foliar and axial development, =II=, 28–33, 57;
foliar development, =II=, 76, 91;
branch symmetry, =II=, 145;
cell metamorphoses, =II=, 176;
tissue differentiation, =II=, 244, 246, 251, 252, 256, 272,
385–6;
adaptation of reproductive activity to conditions, =II=, 289;
integration, =II=, 292;
indefiniteness, =II=, 295;
genesis and development, =II=, 463.

Alimentary canal: metabolic processes and agents, =I=, 68–9, 74;
structural traits, =I=, 192;
progressive development, =I=, 195;
relation to environment, =I=, 196;
function, =I=, 205;
segmentation in annelids, =II=, 125;
differentiation, =II=, 301, 302, 321–2, 323–5, 389;
specializations in birds, =II=, 325;
in ruminants, =II=, 327–9;
differentiation of liver, =II=, 329–33;
muscularity, =II=, 364.

Allotropism: of organic constituents, =I=, 4, 9;
muscular action, =I=, 59.

Alloys, melting point of, =I=, 339.

Alternation of generations, misleading application of term, =II=,
84.
(_See_ Agamogenesis _and_ Gamogenesis.)

Amitosis, occurrence of, in morbid tissues, =I=, 264.

Ammonia: properties, =I=, 7, 9;
nerve stimulation, =I=, 55.

_Amœba_: central development, =I=, 163;
a primary aggregate, =II=, 86;
symmetry of encysted, =II=, 186;
symbiosis, =II=, 400.

_Amphibia_: classification of, =I=, 392;
embryonic respiratory system, =I=, 457;
structure and media, =I=, 483;
limb locomotion, =II=, 15;
segmentation, =II=, 122, 225;
outer tissues, =II=, 311;
respiration, =II=, 334, 338;
Owen on skeleton, =II=, 552, 557, 558.

_Amphioxus_: separation of segmentation spheres of egg, =I=, 691;
embryogeny, =II=, 121;
local segmentation, =II=, 125–7, 605;
genesis of vertebrate axis, =II=, 213–6, 218, 222;
development, =II=, 564.

_Amphipnous cuchia_, vascular air-sacs, =II=, 337.

_Anabas scandens_, the climbing fish, =I=, 480, 483.

_Anacharis_ (see _Eloidea_).

Anæsthetics, diverse effects of, =I=, 55.

_Angræcum_, assimilative function of root, =II=, 255.

“Animal Spirits,” vitalism and, =I=, 115.

Animals: nutrition and molecular re-arrangement, =I=, 36–7;
nitrogenous character, =I=, 39–41;
sensible motion, =I=, 57;
metabolism, =I=, 62–77;
multiplication of energies, =I=, 75;
contrasted traits of plants and, =I=, 196;
what is an individual? =I=, 246–7;
solar influence, =I=, 500, 556;
geologic changes affecting, =I=, 501–4, 549, 550, 556;
interdependence with plants, =I=, 504–6, 514; =II=, 398–401;
complexity of influences affecting, =I=, 506;
geographical isolation and origin of species, =I=, 568–9;
vital attributes, =I=, 577–9;
distribution and antiquity of plant and animal types, =II=, 297;
mutual dependence of organisms at large, =II=, 397–408;
hypothetical plant-animal type, =II=, 397;
progressive increase of size, =II=, 401;
laws of multiplication, =II=, 411–6;
rhythm in numbers, =II=, 419;
law of weights and dimensions, =II=, 434.

Animals, domesticated: variation, =I=, 324, 326, 560, 563, 693;
interbreeding, =I=, 345–7, 354; =II=, 615;
pure and mixed breeds, =I=, 354, 625.

_Annelida_: phosphorescence, =I=, 50;
axial development, =I=, 165, 166;
integration, =I=, 363;
larval forms and phylogeny, =I=, 447; =II=, 115;
segmental fission, =I=, 588–9;
segmentation, =I=, 98–101, 103–4, 602–5; =II=, 107–9, 125–7;
lateral gemmation, =II=, 105;
embryogeny, =II=, 119;
bilateral symmetry, =II=, 197–200;
genesis, =II=, 444, 453.

_Annulosa_: regeneration, =I=, 361–2;
distinctive traits, =I=, 392;
origin of type, =II=, 98–110, 602–6;
unit of composition, =II=, 105;
application of term, =II=, 111;
vertebrate symmetry compared, =II=, 203–6;
segmental differentiation, =II=, 207–9;
unintegrated function in _Planaria_, =II=, 373;
development and genesis, =II=, 464;
nutrition and genesis, =II=, 490.
(See also _Annelida_ and _Arthropoda_.)

Anthropomorphism, former prevalence of, =I=, 419.

Ants: utilization of aphids, =I=, 660–1; =II=, 403, 405;
nest-mates, =II=, 405;
castes in social species, =I=, 658–9, 670, 675;
loss of self-feeding instinct in Amazons, =I=, 660–1, 663–4;
monstrous development of Honey-ants, =I=, 683;
bulk and fecundity, =II=, 492.
(See also _Termites_.)

_Aphis_: individuality, =I=, 249, 250; =II=, 603;
parthenogenesis, =I=, 274–5, 289;
fertility, =I=, 582, 640–1; =II=, 476, 490;
utilized by ants, =I=, 660–1; =II=, 403, 405;
over-multiplication checked by lady-bird, =II=, 406.

Aquatic animals, large size attained by, =I=, 156.

_Arachnida_: avoidance of danger, =I=, 92;
oviparous homogenesis, =I=, 271;
segmentation, =I=, 469; =II=, 113, 114;
integration and homology, =II=, 111, 121;
bilateral symmetry, =II=, 198.

_Arcella_: symmetry, =II=, 186;
outer tissue differentiation, =II=, 309.

_Archegoniateæ_: morphological composition, =II=, 32–5;
growth and development, =II=, 50–6;
tubular structure, =II=, 58, 62;
alternating generation not distinctive, =II=, 84;
asymmetry and environment, =II=, 140;
integration, =II=, 293, 296;
individuation and genesis, =II=, 441, 451, 463.

Archenteron: primitive externality, =II=, 301;
formation of cœlom, =II=, 302.

_Archiannelida_: segmentation, =II=, 125.

_Arenicola marina_: polytrochal larvæ, =II=, 109.

Arm: embryogeny of human, =I=, 169;
vicarious use of, =I=, 209.

Army, morphological analogy, =II=, 6.

Arteries (_see_ Vascular System).

_Arthropoda_: uniaxial development, =I=, 165;
protoplasmic continuity, =I=, 190, 629;
excursiveness, =I=, 481;
limb locomotion, =II=, 15;
integration and homology, =II=, 111–4, 121;
bilateral symmetry, =II=, 197–200;
genesis, =II=, 445, 453.

Ascidians: multiaxial development, =I=, 165, 166;
functional differentiation, =I=, 202;
composite individuality of _Doliolum_, =I=, 247;
self-fertilization, =I=, 342;
integration, =II=, 94, 96, 97;
symmetry, =II=, 194;
origin of vertebrate type, =II=, 194, 598, 605.

_Ascomycetes_, reproduction, =II=, 450.

Assimilation: compared with reasoning, =I=, 81–7;
a trait of vitality, =I=, 577.

_Asteroidea_, radial symmetry, =II=, 196.

Astronomy: growth of celestial bodies, =I=, 135;
Schleiden on individuality, =I=, 245;
evolution, =I=, 432, 435;
classification of stars, =I=, 444;
rhythm of, and organic change, =I=, 499–501, 557;
law of equilibration, =I=, 519–20;
co-operation of structure and function, =II=, 3.

Atavism: occurrence of, =I=, 305–6, 314;
digital variation, =I=, 321–3.

Atoms: use of term, =I=, 6, 31;
ethereal undulations and oscillations, =I=, 31–5.

Australia: settler’s usages, =I=, 364;
ratio of jaw to skull in natives, =I=, 541.

Axillary buds, origin and development, =II=, 65–8.

Axis: “neutral” of mechanics, =II=, 210;
genesis of vertebrate, =II=, 212–6, 224–7.

_Bacteria_: fission, =I=, 270;
non-nucleated, =II=, 20;
rate of increase, =II=, 443.

Baer, K. E. von: embryological formula, =I=, 171, 172, 451, 453,
461, 466;
zoological classification, =I=, 383;
on animal transitions, =I=, 480.

_Balanophoræ_, inner tissue, =II=, 274.

Bark: varied development, =II=, 247–9;
physiological differentiation, =II=, 249–50, 258, 386.

_Basidiomycetes_, reproduction, =II=, 450.

Bat, infertility of, =II=, 473.

Bates, H. W., protective mimicry of butterflies, =I=, 398.

_Batrachia_ (see _Amphibia_).

Bean, vascular system, =II=, 573, 591.

Beaver, tail and co-adapted structures, =I=, 616.

Bees (_see_ Insects).

_Begoniaceæ_: multiplication =I=, 224, 317, 442;
individuality, =I=, 251;
development from scales, =I=, 282;
symmetry, =II=, 159, 166;
development, =II=, 271.

Berkeley, M. J., indefiniteness of mosses and ferns, =II=, 296.

Bile, arrest of excretion, =I=, 209.

Bilirubin and biliverdine, function of, =II=, 330, 333.

Biology: definition and divisions, =I=, 124–5;
organic structural phenomena, =I=, 125–7;
also functional, =I=, 127–9;
actions and reactions of function and structure, =I=, 129–30;
genesis, =I=, 130–1;
limited knowledge of, =I=, 131;
evolution, =I=, 432, 434;
sociological analogies (_see_ Sociology).

Biophors, Weismann’s germ-plasm units (_see_ Weismann).

Birds: flesh-eating and grain-eating contrasted, =I=, 68;
growth and expenditure of force, =I=, 142;
size of egg and adult, =I=, 144;
limitations on flight, =I=, 155;
self-mobility, =I=, 175;
temperature, =I=, 176;
functional and structural differentiation, =I=, 201;
food of starving pigeon, =I=, 215;
viviparousness, =I=, 271;
heredity and pigeon breeding, =I=, 305;
atavism in pigeon, =I=, 314;
osseous variation in pigeon, =I=, 321;
classification, =I=, 392;
migrations and change of habits, =I=, 399, 402, 500;
distribution in time, =I=, 410;
Darwin on petrels, =I=, 455;
rudimentary teeth, =I=, 457;
vertebræ, =I=, 471; =II=, 564;
feather development, =I=, 473;
habits of water ouzel, =I=, 485;
egg shells and direct equilibration, =I=, 526;
bones of waders and direct equilibration, =I=, 527;
fertility and nervous development, =I=, 598;
cellular continuity, =I=, 629;
adaptation of structure to environment, =II=, 12;
sexual selection, =II=, 269;
wing spurs, =II=, 313;
outer tissue differentiation, =II=, 314–5, 387;
alimentary canal development, =II=, 325, 327;
muscular colour and activity, =II=, 365–9;
nutrition, =II=, 433;
cost of genesis, =II=, 436;
growth and genesis, =II=, 454, 458;
heat expenditure and genesis, =II=, 468–9, 474;
activity and genesis, =II=, 470–2, 474;
contrasted mammalian fertility, =II=, 470;
eggs of wild and tame, =II=, 478;
fertility of blackbird and linnet compared, =II=, 503;
Owen on skeleton of, =II=, 559, 560, 561.

Bischoff, embryogeny of human arm, =I=, 169.

Bison, modifications entailed by increased weight of head, =I=,
512.

Blackbird, contrasted with linnet in development, =II=, 503.

Blainville, de, definition of life, =I=, 79, 93.

Blastosphere, independence of cells in Echinoderm larvæ, =I=, 185.

Blastula, definition of life and formation of, =I=, 112.

Blood: similarity of iron peroxide, =I=, 17;
metabolic processes, =I=, 69;
segregation of abnormal constituents, =I=, 180;
protozoon life of corpuscles, =I=, 186–7;
morbid changes, =I=, 221, 701;
assimilative power and organic repair, =I=, 221–2;
respiratory tissue differentiation, =II=, 310–1;
pressure in mammals, =II=, 340.
(_See also_ Vascular System.)

Blow-fly, Weismann on nutrition and genesis in, =I=, 678–9.

Boers, Cape, habits and fertility, =II=, 508.

Boismont, A. B. de, on human fertility, =II=, 511.

Bone: growth and function, =I=, 151;
adaptability, =I=, 230; =II=, 217–8;
function and weight, =I=, 308, 693;
mammalian cervical vertebræ, =I=, 394;
evolution and vertebral column, =I=, 470–1;
partial development, =I=, 473;
size of head as influencing, =I=, 512, 536–9;
direct equilibration and strength, =I=, 527;
natural selection and co-adaptations, =I=, 614–21, 674, 677;
rudimentary limbs of whale, =I=, 668, 685, 692;
inheritance of acquired modifications in Punjabis, =I=, 689;
skull development, =II=, 222;
theory of supernumerary, =II=, 223;
Cope on origin of vertebrate osseous system, =II=, 225–7;
differentiation, =II=, 344–56;
false joints, =II=, 370–2;
Owen’s theory of vertebrate skeleton, =II=, 548–66.

Book-worm, food of, =I=, 77.

Born, G., experiments on frog larvæ, =I=, 365.

Botany, biological classification, =I=, 124, 125.
(_See_ Plants.)

_Bothriocephalus_, development, =II=, 490.

_Botryllidæ_: development, =I=, 166;
independence of components, =I=, 247;
agamogenesis, =I=, 641.

Bower, Prof., on alternation of generations, =II=, 84.

_Brachiopoda_, rude vascular system, =II=, 340.

Bradbury, J. B., on vaso-dilators, =I=, 55.

Brain: natural selection and mental evolution, =I=, 553;
analysis of substance, =I=, 596;
weight in higher animals, =I=, 598–9;
size in civilized and uncivilized, =II=, 530.

Branches (_see_ Morphology).

_Branchiæ_ (_see_ Respiratory System).

Brass, effect of antimony on, =I=, 121.

Bread, diamagnetism, =I=, 370.

Breeding: heredity, =I=, 304–5;
in-and-in, =I=, 344–7, 353; =II=, 615;
pure and mixed, =I=, 354, 625.

Bricks, changed equilibrium shown by, =I=, 38, 42.

Brodie, T. G., cell chemistry, =I=, 260.

Brownell, Miss J. L., on birth-rate in United States, =II=, 520.

Brown-Séquard, on inherited epilepsy, =I=, 312, 624.

_Bryophyllum_, peculiar proliferation, =II=, 295.

_Bryophyta_, large size attained by some, =I=, 138.

_Bryozoa_, gemmation, =I=, 588.

Budding (_see_ Gemmation).

Buds: development, =I=, 167–8;
theories of heredity and cauline, =I=, 358–9, 360;
axillary, =II=, 65–9;
effects of nutrition, =II=, 73–4.

Butterfly: protective mimicry, =I=, 398;
instance of tame, =I=, 684.

Cabbage, varieties of, =I=, 302.

_Cactaceæ_: foliar and axial development, =II=, 47–9;
differentiation in, =II=, 258, 276, 282;
vascular system, =II=, 282;
dye permeability and circulation, =II=, 571, 572;
wood formation, =II=, 575, 577, 578, 580.

“Callus,” budding from, =I=, 358, 359.

Camel, natural selection and hump of, =I=, 534.

Canadians, French, fertility of, =II=, 509.

Cancer, the definition of life, =I=, 111;
œsophageal, =II=, 324;
and vascular system, =II=, 343.

Caoutchouc, leaf-structure, =II=, 589.

Capillaries (_see_ Vascular System).

Capillarity, and vegetal vascular system, =II=, 279–80, 286, 568,
570, 585, 587, 592–6.

Carbohydrates: instability, =I=, 10;
the term “hydro-carbon,” _ib._;
molecular changes in, =I=, 42–3;
organic transformation, =I=, 43, 48;
metabolic processes, =I=, 63–77, 262–3; =II=, 362.

Carbon: properties, =I=, 3–5, 20;
compounds, =I=, 6, 7, 9, 10–12, 13, 24–5.

Carbonic acid (carbon dioxide): properties, =I=, 6, 7, 9;
in animal and plant functions, =I=, 62, 214; =II=, 398;
diffusibility, =II=, 331.

Carbonic oxide, properties, =I=, 6.

Carnivores: nitrogenous food, =I=, 47, 68;
katabolic process, =I=, 71;
restricted environment, =I=, 396;
their beneficial effects on animal life, =II=, 405–6.

Carpenter, W. B.: on functional specialization, =I=, 208;
reproduction of seaweed, =I=, 582;
vegetal cell multiplication, =I=, 585;
structure and multiplication of compound organisms, =I=, 586–9;
on fundamental traits of sex, =I=, 595;
nutritive system of invertebrates, =I=, 595;
_Macrocystis_, =II=, 450;
nutrition and reproductive function, =II=, 460.

Cartilage (_see_ Bone).

Castration, effect of, on growth, =II=, 459.

“Castration parasitaire,” Julin on, =II=, 493–6.

Catalysis, and vital metamorphosis, =I=, 39, 43.

Cattell, McKeen, on tactual perceptiveness, =I=, 666.

_Caulerpa_, simulation of higher plant-forms, =II=, 22.

Cave-animals, degeneration of eyes, =I=, 309, 612–3, 614, 647–9,
693.

Cell, the: incomprehensibility of forces at work in, =I=, 118;
protoplasts and their traits, =I=, 181;
the cell-theory, =I=, 184, 252; =II=, 17–21, 85;
differentiation, =I=, 188–9, 194;
the continuity of protoplasm, =I=, 190–2, 194, 628–30; =II=, 21;
its structure, =I=, 253–5;
function of centrosome, =I=, 254–5, 257;
structure and function of nucleus, =I=, 255–6, 258–9;
karyokinesis, =I=, 257–8;
function of chromatin, =I=, 259–65;
fertilization and function of polar bodies, =I=, 266–8;
theories of heredity based on theory, =I=, 356;
Weismann’s differentiation into reproductive and somatic, =I=,
622, 628–30, 633–44;
nucleus absent or dispersed, =II=, 20, 85;
morphological differentiation, =II=, 175–7;
animal morphology, =II=, 228–30;
morphological summary, =II=, 233;
vegetal tissue differentiation, =II=, 249–50, 386;
vascular development, =II=, 279–84, 389.

Centipede, bilateral symmetry, =II=, 198–200.

_Cephalopoda_: bilateral symmetry, =II=, 203;
vascular system, =II=, 341.

_Cercariæ_ (see _Distoma_).

_Cereus_, tissue differentiation, =II=, 276, 283.

Cesalpino, =I=, 377.

_Cestoda_ (see _Entozoa_).

_Chætopoda_, segmentation, =II=, 98, 103, 605.

_Chaja_, wing spurs, =II=, 313.

Change, and definition of life, =I=, 81–90, 113.

Charles, R. H., on inheritance of acquired modifications in
leg-bones of Punjabis, =I=, 689.

Chatié, on single and double stocks, =II=, 622.

Chemistry: properties of organic elements, =I=, 3–5, 20, 22;
of diatomic compounds, =I=, 7–10;
tri-atomic, =I=, 10–12;
poly-atomic, =I=, 12–13, 25;
traits of evolution, =I=, 23–4;
ethereal undulations and atomic oscillation, =I=, 31–6;
chemical affinity and organic change, =I=, 36–7, 38–43;
oxidation and generation of heat, =I=, 46–9, 60;
generation of nerve force, =I=, 52, 60;
metabolism, =I=, 62–77;
physiology and organic, =I=, 127;
flesh constituents, =I=, 154;
composition of organisms and environment, =I=, 173;
organic development and differential assimilation, =I=, 179–80;
chemical units, =I=, 225; =II=, 612;
primitive ideas of elements, =I=, 417;
evolution of organic compounds, =I=, 696–701, 703.

Chestnut, leaf symmetry, =II=, 149, 153.

_Chiton_: simulation of segmentation, =II=, 116, 118;
symmetry, =II=, 202.

Chlorophyll: function, =I=, 65; =II=, 263;
nutrition and absence of, =II=, 74;
constitution, =II=, 262;
symbiotic presence in animals, =II=, 400.

_Chondracanthus gibbosus_, enormous development of reproductive
system, =II=, 487.

_Chordata_, affinities, =I=, 466.

Chromatin (_see_ Cell).

Circle, the, and evolution hypothesis, =I=, 433.

Circulation (_see_ Vascular System).

_Cirrhipedia_: Darwin on retrograde development, =I=, 458;
remarkable transformation in _Sacculina_, =II=, 494–5.

Civilization, human evolution and genesis, =II=, 529–31.

_Cladophora_: integration, =II=, 25;
axial development, =II=, 28.

Classification: subjective conception, =I=, 78;
two purposes of, =I=, 374;
a gradual process, =I=, 375;
botanical, =I=, 377–80, 389–90;
zoological, =I=, 380–9;
incomplete equivalence of groups, =I=, 389, 445–6, 448, 555, 572;
group attributes, =I=, 390–3;
the truths interpreted, =I=, 393–4;
ethnologic and linguistic evolution, =I=, 441–6;
organic evolution, =I=, 443, 447, 555;
differences in kind and degree, =I=, 444–6;
antecedent structural similarity, =I=, 447, 448–9;
Von Baer’s formula, =I=, 451–4, 555;
organic, not uniserial, =II=, 115.

_Classification of the Sciences, The_, and evolution and
dissolution, =II=, 5.

Claus, C, on segmentation in Annelids and Chætopods, =II=, 605.

Clover: flower and axial development, =II=, 45;
symmetry, =II=, 152.

Co-adaptation of co-operative parts: principles underlying, =I=,
234–5, 511–3, 514–5;
slow operation of the process, =I=, 236;
sociological analogy, =I=, 237–40;
reversion under original conditions, =I=, 240;
the analogy continued, _ib._;
the case of bison’s head, =I=, 512;
natural selection an inadequate explanation, =I=, 535, 614–21,
692;
Romanes on “cessation of selection” as effecting, =I=, 560,
561–2;
Weismann’s theories, =I=, 560–3, 663–5, 670, 674–5;
natural selection and economy of growth, =I=, 562;
physiological processes involved, =I=, 566–7;
Wallace’s argument from artificial selection, =I=, 615;
what are co-operative parts? =I=, 616–7;
“intra-selection” examined, =I=, 676–8.

Coal, social effects of supply, =I=, 238–9, 241.

Cocoa-nut, growth and fertility, =II=, 457.

Coccospheres: vital problem presented by protective structures,
=I=, 119;
imbricated plates, =I=, 182.

Cockroach, ousting of European species, =I=, 399.

Cod: ova of, =II=, 435;
growth and fertility, =II=, 454.

_Codium_: symmetry, =II=, 136;
tissue differentiation, =II=, 246.

_Cœlenterata_: rudimentary contractile organs, =I=, 58;
vital changes in polyp, =I=, 95;
axial development, =I=, 165, 166;
environment and structure, =I=, 173;
self-mobility, =I=, 175; =II=, 14, 15;
functional differentiation, =I=, 201, 391;
inactivity and waste, =I=, 213;
reparative power, =I=, 219, 224;
individuality, =I=, 246, 247, 250;
heterogenesis, =I=, 273, 277, 296;
negative disintegration in _Hydrozoa_, =I=, 276, 587;
reproductive tissue, =I=, 281;
differentiation in _Hydrozoa_, =I=, 391;
classificatory value, =I=, 446;
regeneration of fragments, =II=, 90;
integration, =II=, 90, 102, 105, 124;
gemmation, =II=, 91;
tertiary aggregation, =II=, 92, 95, 124;
molluscan affinities, =II=, 115;
radial symmetry, =II=, 188;
symmetry of compound, =II=, 192–3;
segmental differentiation, =II=, 207;
physiological differentiation in _Hydra_ and analogy, =II=, 300;
ciliation of blastula, =II=, 301;
tissue reduplication, =II=, 301–2, 389;
outer tissue differentiation, =II=, 309;
osmosis in _Hydra_, =II=, 339;
vascular system in _Hydra_, =II=, 340, 376;
functional co-ordination, =II=, 376;
symbiosis, =II=, 400;
asexual genesis, =II=, 443–4;
growth and sexual genesis, =II=, 452;
development and genesis, =II=, 462;
nutrition and genesis, =II=, 476.

Cœlom, origin and function, =II=, 302–3.

Collins, F. Howard, jaws and teeth of savages and civilized, =I=,
541.

Colloids: T. Graham on, =I=, 15–8;
diffusibility, =I=, 18–21;
organic, =I=, 21, 25, 26;
pliability and elasticity, =I=, 27;
capillary affinity, =I=, 28;
isomerism, =I=, 59;
instability, =I=, 350;
molecular mobility and diffusibility, =II=, 331;
instability of, and nerve differentiation, =II=, 356–61;
and muscular tissue, =II=, 361–4.

Colonies, autogenous development and parallel in heredity, =I=,
366–8; =II=, 620.

Colour: sensation of, =I=, 54;
phœnogamic, =II=, 75, 265–6;
light and vegetal, =II=, 261–2;
floral fertilization, =II=, 267–9;
sexual selection, =II=, 269;
activity and muscular, =II=, 365–9;
physiological units and mixture of, in offspring, =II=, 616, 617.

Commensalism, organic Integration as displayed in, =II=, 402–4.

_Compositæ_: floral symmetry, =II=, 173.

Condor, weight of, =I=, 155.

_Confervoideæ_, =I=, 279, 280; =II=, 25, 28, 449.
(See _Algæ_.)

_Conjugateæ_, =II=, 449.
(See _Algæ_.)

Conjugation, in _Algæ_, =I=, 279;
in _Protozoa_, =I=, 280; =II=, 452;
can fission persist without? =I=, 637;
relation to growth, =II=, 449.

Connective tissue, Hertwig’s classification, =I=, 189.

Constitutional units, =I=, 369.
(_See_ Physiological Units.)

Consumption, hereditary transmission, =I=, 307.

Co-ordination of actions (_see_ Life).

Cope, E. D., on origin of vertebrate structure, =II=, 225–7.

_Cormophyta_: slight internal differentiation, =II=, 273;
vascular system, =II=, 280.

_Corpuscula tactus_, their function, =I=, 75.

Correspondence, use of word, =I=, 97.
(_See_ Life.)

Cousin-marriages, =I=, 345; =II=, 615.

Cow: what prompts her to mumble a bone? =I=, 120.

Cow-parsnip (see _Heracleum_).

Crab (see _Crustacea_).

Creation (_see_ Special creation).

_Crinoidea_, symmetry, =II=, 195–6.

Crocodile, continuous growth, =I=, 154, 292.

Crookes, Sir W., hypothetical chemical unit “protyle,” =I=, 22, 23.

_Cruciferæ_, floral symmetry, =II=, 164, 171.

_Crustacea_: locomotion of lobster, =I=, 175;
regeneration of limbs, =I=, 224, 360, 589; =II=, 76;
homogenesis, =I=, 271;
genesis and nutrition in _Daphnidæ_, =I=, 290–1;
growth and genesis, =I=, 292;
degeneration of eye in cave-inhabiting, =I=, 309, 614, 648;
hermit-crab parasite, =I=, 397;
changes of media, =I=, 401, 481–2;
retrograde development in cirripedes, =I=, 458;
segmentation, =I=, 468–9; =II=, 114;
Darwin on jaws and legs, =I=, 471;
survival of cirripedes, =I=, 517;
integration and homology, =II=, 111–4, 121, 603;
bilateral symmetry, =II=, 198–201;
eyes, =II=, 318;
dermal structure of hermit-crab, =II=, 322, 387;
fertility, =II=, 453;
nutrition and genesis in parasitic species, =II=, 487;
“castration parasitaire,” =II=, 493–6.

Crystalloids: Prof. Graham on, =I=, 15–8;
diffusibility, =I=, 18–21;
organic, =I=, 21–2, 26.

Crystals: simulation of life in “storm glass,” =I=, 96;
growth, =I=, 135–7, 577;
segregation, =I=, 179, 221, 223;
equilibration, =I=, 337;
physiological units and polarity, =I=, 701–6;
time and formation, =II=, 77.

_Ctenodrilus_, segmental individuality, =II=, 103, 603, 604.

Cube, bilateral symmetry, =II=, 132.

Cunningham, J. T., =I=, vi; =II=, vi;
on non-adaptive specific characters, =I=, 565;
food of blow-fly larvæ, =I=, 678;
arthropod segmentation, =II=, 114;
egg-production of Conger, =II=, 425.

Cuttle-fish, Individuality of _Hectocotylus_, =I=, 250.

Cuvier, zoological classification, =I=, 381.

Cyanogen, properties, =I=, 7, 9.

_Cyclichthys_, dermal structure, =II=, 306.

Dalyell, Sir J., regeneration in _Dasychone_, =I=, 361;
propagation of _Hydra_, =II=, 476.

_Daphnidæ_, heterogenesis and nutrition, =I=, 290–1.

Darwin, C: _Origin of Species_, =I=, 129; =II=, 528;
natural selection and function, =I=, 308–9, 693;
atavism, =I=, 314;
osseous variations in pigeons, =I=, 321;
plant variation and domestication, =I=, 325;
“spontaneous variation,” =I=, 328, 697;
floral fertilization, =I=, 340; =II=, 168, 267, 407, 608;
intercrossing and self-fertilization, =I=, 344, 345;
intercrossing =I=, 347, 611, 669;
his theory of pangenesis examined, =I=, 356–62, 370, 372;
plant-fertilization and distribution, =I=, 397;
habits of birds, =I=, 400;
distribution and natural barriers, =I=, 402, 476;
disappearance and non-reappearance of species, =I=, 406;
distribution in time and space, =I=, 410;
linguistic classification, =I=, 442;
classification of organisms, =I=, 443;
classification and descent, =I=, 448;
on petrels, =I=, 455;
suppression of organs, =I=, 457;
development of _Cirrhipedia_, =I=, 438;
jaws and legs of _Crustacea_, =I=, 471;
aborted organs, =I=, 474, 563;
relations of species in Galapagos archipelago, =I=, 478;
opinions of E. Darwin and Lamarck, =I=, 491;
the term “survival of the fittest,” =I=, 530;
Indirect equilibration by natural selection, =I=, 530–5;
inheritance of acquired characters, =I=, 535–42, 560, 630, 685,
690;
Wallace on natural selection in man, =I=, 553;
misleading connotations of term “natural selection,” =I=, 609,
695;
caste gradations and jaws of driver ants, =I=, 658;
attachment of climbing plants, =II=, 276–7;
vegetal fructification, =II=, 294;
earth-worm, =II=, 402;
animal sterility and domestication, =II=, 480, 483;
variation in hyacinth and camellia, =II=, 621.

Darwin, Dr. E., modifiability of organisms, =I=, 490, 492–7.

Death: an arrest of vital correspondence, =I=, 102;
only limit to vegetal growth, =I=, 153;
cessation of co-ordination of actions, =I=, 578, 579;
Weismann’s hypothesis, =I=, 636–8;
physiological integration, =II=, 374, 392;
cause of natural, =II=, 413;
relation to births, =II=, 417.

Definiteness: of vital change, =I=, 87–90, 106, 109;
developmental, =I=, 178;
functional, =I=, 212;
segregation of evolution, =I=, 514–6.

Definition, difficulties of, =I=, 78; =II=, 17.

Degeneracy, morphological obscurations due to, =II=, 12, 13.

_Dendrobium_ (_see_ Orchids).

_Desmidiaceæ_: unicellular, =II=, 21;
linear and central aggregation, =II=, 23;
natural selection and symmetry, =II=, 134, 133;
morphological differentiation, =II=, 177;
tissue, =II=, 244;
genesis, =II=, 440, 449.

Determinants, Weismann’s germ-plasm units (_see_ Germ-plasm).

Development: an increase of structure, =I=, 162; =II=, 461;
primarily central, =I=, 162, 166;
uni- and multicentral, =I=, 163–4, 166–7;
axial, =I=, 164, 167;
uni- and multiaxial, =I=, 165–6;
a change to coherent definite heterogeneity, =I=, 167–70, 179;
Von Baer’s formula, =I=, 171–2;
individual differentiation from environment, =I=, 172–8;
cell-formation, =I=, 225;
discontinuous, and agamogenesis, =I=, 275;
Prof. Huxley’s classification, =I=, 276;
sociological parallel to autogenous, =I=, 364–8; =II=, 620;
retrograde, =I=, 457–8;
inequalities among co-operative parts, =I=, 617;
“heterochrony,” =I=, 655;
continuous and discontinuous vegetal, =II=, 52;
summary of physiological, =II=, 384–90;
nutrition and genesis, _résumé_, =II=, 497–9;
evolution, =II=, 501–5;
commencement of genesis, =II=, 506;
of vertebrate limbs, =II=, 553.
(_See also_ Multiplication.)

_Development Hypothesis, The_, =I=, 417.

Dialects (_see_ Language).

Dialysis, and diffusibillty. =I=, 19, 20.

Diastase, decomposition of, =I=, 38, 40.

_Diatomaceæ_: tissue, =II=, 244;
genesis, =II=, 440, 448.

Diatomic compounds (_see_ Chemistry).

Dicotyledons: growth, =I=, 139, 143; =II=, 63–4, 69–72, 78, 82–3;
uniaxial development, =I=, 165;
stem and leaf functions, =II=, 257;
mechanical stress and wood formation, =II=, 277;
growth and genesis, =II=, 451.

Differentiation (_see_ Morphology _and_ Physiology).

_Difflugia_: primary aggregate, =II=, 86–7;
symmetry, =II=, 186;
outer tissue differentiation, =II=, 309.

Diffusion, of colloids and crystalloids, =I=, 18–20; =II=, 331.

Digestion: action of nitrogenous compounds, =I=, 69;
obesity, =II=, 480–4;
fertility, =II=, 514.

Dimorphism: floral, =I=, 534;
sexual, in parasites, =I=, 315;
social insects (_see_ Insects).

Dinosaurs, size of, =I=, 139.

_Diphyes_: individuality, =I=, 246;
symmetry, =II=, 192.

Disease: segregation of blood constituents, =I=, 179;
changes in blood from, =I=, 221, 701;
heredity, =I=, 306–7, 312–3, 622–3;
belief in supernatural origin, =I=, 419;
parasitism and special creation, =I=, 427;
morbid products as specific characters, =I=, 567;
telegony, =I=, 646;
dermal structure, =II=, 306;
intestinal muscular hypertrophy, =II=, 325;
indigestion and alimentary canal development, =II=, 328;
jaundice and bilirubin, =II=, 330;
localization of excretion, =II=, 331;
membranes in inflammatory, =II=, 343;
osseous differentiation in rickets, =II=, 352;
fatty degeneration, =II=, 482.

Disintegration, physiological (_see_ Physiology).

_Distoma_: metagenesis, =I=, 273–4;
disintegration of genesis, =I=, 276;
cycle of generations, =II=, 489.

Distribution: physical limits, =I=, 396;
organic environment, =I=, 396–8;
parasitic conditions, =I=, 397–8;
simultaneity of agencies affecting, =I=, 398;
mutual encroachments of species, =I=, 398–401, 477, 489;
facts disproving pre-adaptation to habitats, =I=, 401–3, 411–2;
of animals and plants in time, =I=, 404–11, 412;
ousting of native species in New Zealand, =I=, 477;
local influences, =I=, 477–9, 489;
through varied media, =I=, 479–85, 489, 556;
past and present organic forms, =I=, 485–9, 556;
complex organization and, =II=, 296–7.

Division of labour, physiological (_see_ Labour).

Dog: contrasted lives of tortoise and, =I=, 103, 104;
inherited habits, =I=, 309, 573;
abnormal digits, =I=, 324;
interbreeding of divergent varieties, =I=, 565;
decrease of jaw, =I=, 615, 693;
telegony, =I=, 645;
conditions affecting fertility, =II=, 474, 479.

Dohrn, theory of vertebrate structure, =II=, 606.

_Doliolum_, combination of individualities, =I=, 247.

Domestication (_see_ Animals).

Doubleday, E., on nutrition of genesis, =II=, 510–2.

Driesch, separation of segmentation spheres of _Echinus_ ovum, =I=,
691; =II=, 618.

Dropsy (_see_ Disease).

_Drosera_: individuality, =I=, 251;
proliferous growth, =II=, 75.

Du Bois-Reymond, E. H., electricity from muscles and nerves, =I=,
50.

Dumas, antithesis of animals and plants, =I=, 62.

Dwarfs, Hindu family of, =I=, 316.

Ear, development of vertebrate, =II=, 318, 320.

Earth, climatic rhythm and organic change, =I=, 499–501, 557.

Earth-worm: bilateral symmetry, =II=, 199, 200;
mould production, =II=, 402.

_Echinococcus_ (see _Entozoa_).

_Echinodermata_: independence of blastosphere cells, =I=, 185;
protoplasmic continuity in embryos, =I=, 190;
separation of segmentation spheres of ovum, =I=, 691; =II=, 618;
symmetry, =II=, 191, 195–6.

Economy: of growth in natural selection, =I=, 536, 562;
a trait of organic evolution, =II=, 501, 504.

Ectoderm: functional differentiation, =I=, 202, 203;
functional vicariousness, =I=, 209;
reproductive function, =I=, 281.

Effects, Multiplication of: variation, =I=, 329–30, 333;
organic evolution, =I=, 511–4, 515, 517, 549, 557; =II=, 405–6;
morphological development, =II=, 7–9, 234;
physiological differentiation, =II=, 390–1, 392.

Eggs (_see_ Embryology).

Eimer, T., theory of orthogenesis, =I=, 563–4.

_Elasmobranchii_: protoplasmic continuity, =I=, 629;
segmentation, =II=, 126.

Electricity: genesis in organic matter, =I=, 50–2, 60;
muscular action, =I=, 59;
incomprehensibility, =I=, 121.

Elephant: fertility, =I=, 583, 599; =II=, 459, 506;
cerebro-spinal system, =I=, 598, 599.

Elk, Irish, horns and correlated parts, =I=, 537, 674.

_Eloidea canadensis_: individuality, =I=, 248;
enormous agamic multiplication, =I=, 642.

Elongation, and locomotion in animals, =II=, 15.

Embryology: as aiding biology, =I=, 125–6;
simulated growth, =I=, 136;
initial and final organic bulks, =I=, 143, 158, 161;
fœtal flesh constituents, =I=, 154;
human arm development, =I=, 169;
Von Baer’s formula, =I=, 170–2, 451–4, 466;
embryonic heat, =I=, 177;
spherical organic form, =I=, 177;
unit-life in multicellular organisms, =I=, 185–6;
functional differentiation, =I=, 203;
individuality, =I=, 246–7;
unspecialized reproductive tissue, =I=, 279–83, 317;
changes following impregnation, =I=, 283–4;
nutrition and vegetal growth, =I=, 285–8, 295–7;
and animal growth, =I=, 289–94, 295–7;
physiological units and heredity, =I=, 317–9;
variation and parental functional condition, =I=, 324;
uterine environment, =I=, 327–8;
physiological units and variation, =I=, 330–4, 458;
fertilized and unfertilized ova, =I=, 340–1;
hermaphrodism, =I=, 341–2, 344;
sociological parallel, =I=, 366–8;
evolution hypothesis, =I=, 434, 436, 453, 454, 555;
petrel development, =I=, 455;
substitution and suppression of organs, =I=, 456–8, 466, 472–3;
structural proclivities of physiological units, =I=, 458;
abridgment of stages, =I=, 458–9, 464;
disappearance of intermediate forms, =I=, 459–60, 463;
pre-adaptation, =I=, 461–3;
discrimination of species in early stages, =I=, 461;
anomalous persistence of ancestral traits, =I=, 463–5;
phylogeny, =I=, 486;
egg-shell function, =I=, 527;
genesis of grades in social insects, =I=, 654–6, 658–9, 679–80;
determination of sex, =I=, 657;
order of development qualified by needs, =I=, 679;
osteology of Punjabis, =I=, 689;
direct transformations and physiological units, =I=, 706;
transformation of blastema, =II=, 20;
arrest of growth and innutrition, =II=, 73;
development of segmented animals, =II=, 100–2, 602;
adaptive vertebrate segmentation, =II=, 118–23, 124, 223–4,
605–6;
animal cell morphology, =II=, 228;
primary differentiations of germinal layers, =II=, 300–2;
lung development, =II=, 333–4;
mammalian ova-maturation, =II=, 342–3;
movements of ova, =II=, 356, 363;
modifications in mole, =II=, 391;
genesis and nutrition, =II=, 424, 425;
fish ova, =II=, 435, 454;
cost of genesis, =II=, 435–6;
number of birds’ eggs, =II=, 454–6, 478;
heat and genesis, =II=, 468, 474;
activity and genesis in birds, =II=, 470–2, 474;
vertebrate limb development, =II=, 553;
ossification in vertebrates, =II=, 556;
Owen’s vertebrate theory, =II=, 563;
development of vertebræ, =II=, 564.
(_See also_ Multiplication.)

Embryology of conceptions, =I=, 451.

Emigrants, type of organization among, =I=, 364; =II=, 620.

Endoderm: functional differentiation, =I=, 202, 203;
functional vicariousness, =I=, 209.

Endogen, application of term, =II=, 62, 78, 82.
(_See_ Monocotyledons.)

Energy: evolution of, in animals, =I=, 71–7;
organic growth and expenditure, =I=, 141;
functional transfer, =I=, 201–6;
chromatin as the source of, in karyokinesis, =II=, 261–5.
(_See also_ Force.)

_Entozoa_: metagenesis, =I=, 273, 641;
self-fertilization, =I=, 342;
distribution, =I=, 398;
and special creation, =I=, 428;
fission in simple types, =I=, 584;
nutrition and genesis, =I=, 641; =II=, 488;
direct transformation, =I=, 706;
integration, =II=, 102;
segmentation, =II=, 107, 108;
interdependence and organic integration, =II=, 404.

Environment: degree of life and complexity of, =I=, 104–7;
relation to organic structure and function, =I=, 172–8; =II=,
12–5;
adaptation to varied media an evidence of evolution, =I=, 479–81,
556;
influence of solar system, =I=, 500, 556;
inherited adaptation to, =II=, 623.

_Eolis_, branchiæ, =II=, 118.

Epidermis (_see_ Skin).

Epilepsy: definition of life and movements in, =I=, 112;
heredity, =I=, 312.

Epithelium: ciliated, =I=, 187;
Hertwig’s classification, =I=, 189;
reproductive function, =I=, 280;
“pavement” and “cylinder,” =II=, 229.

_Epizoa_: distribution, =I=, 398;
special creation and effects of, =I=, 428;
interdependence and organic integration, =II=, 404;
nutrition and genesis, =II=, 487.

Equilibration: variation and law of, =I=, 326, 334;
molecular arrangement, =I=, 337–45;
of organic change, =I=, 348, 347, 557;
direct and indirect, =I=, 519–22, 573;
adaptation by direct, =I=, 522–3, 551, 557;
nutrition, defence, and fertilization of plants, =I=, 523–5;
direct of animals, =I=, 525–8, 551, 557;
natural selection and indirect, =I=, 530–4, 552, 557;
of natural selection, =I=, 543–7, 552–3, 557;
increasing importance of direct, =I=, 553;
of forces acting on species, =I=, 571–2; =II=, 417–20;
phenomena not accounted for by, =I=, 573;
tissue differentiation, =II=, 245;
genesis of nervous system, =II=, 307–8;
functional, =II=, 391–4;
laws of multiplication, =II=, 411–6;
in human and social evolution, =II=, 537.
(_See also_ Acquired characters _and_ Natural selection.)

Errera, L., on inherited adaptation to environment in Aspergillus,
=II=, 623.

Ethnology: heredity, =I=, 303–4, 310;
plasticity of mixed races, =I=, 354;
primitive ideas, =I=, 417;
evolution and classification, =I=, 441–3, 446;
natural selection, =I=, 553.

_Euphorbiaceæ_: foliar and axial development, =II=, 47–8;
physiological differentiation, =II=, 258;
dye permeability and circulation, =II=, 571;
wood formation, =II=, 575, 577, 578;
foliar vascular system, =II=, 589–92, 596.

Evaporation: organic change, =I=, 28;
vegetal circulation, =II=, 587.