Chapter XXVII: Appendix: To Ctenophora (10)

Wager, on Euglenaceae, 125
Wagner, 256 n.
Wallich, on Protozoa, 45
_Walteria_, 199, _202_;
_W. flemmingi_, 206;
_W. leuckarti_, 206
Wasielewski, on Sporozoa, 94 n.
Water in protoplasm, 12
Water-Fleas, Vorticellidae found on, 158;
rheotaxy of (small Crustacea), 21
Water-vascular system, 428;
of _Asterias rubens_, 441;
of Asteroidea, 457;
of _Ophiothrix fragilis_, 486;
of _Echinus esculentus_, 516;
of _Echinarachnius parma_, 546;
of _Echinocardium cordatum_, 551;
of _Holothuria nigra_, 564;
of Holothuroidea, 568;
of Synaptida, 568;
of Molpadiida, 568;
of Elasipoda, 568;
of _Psolus_, 569;
of _Antedon rosacea_, 583;
of Carpoidea, 597
Weltner, 177, 178
White Ants, hosts of Trichonymphidae, 123
White Man's Grave, 106
Wille, on Volvocaceae, 119
Willey, 194 n., 248, 421, 422
Williams, on density of living protoplasm, 13 n.
Williamson, on structure of Foraminifera, 62
Wilson, on protoplasm, 3 n.;
on syngamy, 34 n.
Wilson, on Sponges, 171, 231
Woltereck, 302
Wolters, on reproduction of _Monocystis_, 96 n.
Woodcock, on association and conjugation in Gregarines, 99 n.;
on Haemoflagellates (= Trypanosomidae), 119 n.
Worms, Earth-, hosts of _Monocystis_, 95
Wreath, adoral, peristomial, of cilia or membranellae of Ciliata
Trichostomata, 137 f.;
of _Stylonychia mytilus_, 139 f.;
of _Metopus_, 154;
of _Caenomorpha uniserialis_, 155;
of Vorticella, 156, 157;
posterior, of _Vorticella_, 156, 157
_Wrightella_, _351_
Wrisburg, on organisms of putrefaction, 43
Würmchen, of Gaule, a name for _Lankesterella_, 102

_Xenaster_, _476_
_Xenia_, 331, 335, 346, _348_
Xeniidae, _348_
_Xenospongia patelliformis_, _216_
_Xiphacantha_, _78_, 78
_Xiphigorgia_, _357_

Yaws, 121 n.
Yellow-cells (= _Zooxanthella_), 80, 86, 125, 261, 373, 396
Yolk-granules of ovum of Sea-urchin, 7
Young state of _one_ pairing-nucleus essential, 34
_Yvesia_, 224

Zambezian Tick, infects man with _Treponema_, 121 n.
Zaphrentidae, _406_
_Zaphrentis_, _407_
Zederbauer, on syngamy in Dinoflagellates, 131 n.
Zittel, 241 n.
Zoantharia, _329_, _365_ f.;
age, 375;
food, 373;
form, 366;
gonads, 369;
mesenteries, 366 f., 368;
mesenteric filaments, 369;
reproduction, 371;
skeleton, 370;
stomodaeum, 369;
tentacles, 366
Zoanthidae, _404_
Zoanthidea, 370, _404_ f.
_Zoanthus_, _405_;
_Z. macgillivrayi_, 406;
_Z. sulcatus_, 406
Zonarial Radiolaria, 75
_Zoochlorella_, _111_;
a Chlamydomonad, 126;
symbiotic, in Heliozoa, 73;
in _Paramecium bursaria_, 153;
in _Stentor polymorphus_, 154;
in _Ophrydium_, 158;
in _Ephydatia_, 175;
in _Hydra viridis_ (= chlorophyll corpuscles), 256
Zooids of _Volvox globator_, 127
Zoosporeae, _89_
Zoospores, of Algae and Fungi, possess contractile vacuole, 15;
of Lower Plants, 17 f.;
of Sarcodina, 49;
of _Trichosphaerium_, 54;
of _Microgromia socialis_, 60;
of Foraminifera, 67 f.;
of _Clathrulina_, 73;
of Radiolaria, 85 f.;
of _Zooxanthella_, 86;
of Acrasieae, 90;
of _Didymium_, 92;
of _Paramoeba eilhardii_, 116 n.
_Zoothamnium_, _138_, 158
_Zooxanthella_, _110_;
a Chrysomonad, 125;
in Radiolaria, 80, 86;
in _Vorticella sertulariae_, 125;
in _Millepora_, 261;
in Zoantharia, 373 f.;
in Madrepores, 396
Zopf, on Monadineae (Flagellates and Proteomyxa), 40
_Zoroaster_, _474_
Zoroasteridae, 454, _474_
_Zostera_, 422
Zygophiurae, 491, _494_, _495_ f., 502
_Zygophylax_, _280_
Zygote, 37 f.;
_Amoeba coli_, 57;
_Centropyxis aculeata_, 57;
_Chlamydophrys stercorea_, 57;
Foraminifera, 69;
_Actinophrys sol_, 72;
_Actinosphaerium_, 75;
Gregarinidaceae, 95 f., 97;
Coccidiaceae, 97, 100 f.;
_Coccidium_, 100, 101 f.;
Acystosporidae, 97, 104 f.;
Flagellata, 116 n., 117 f.;
_Bodo saltans_, 117 f.;
Dinoflagellata, 131 n.;
Ciliata, 148 f.
—see also Coupled cell, Fertilised egg, Ookinete, Oosperm, Oospore,
Zygotospore
Zygotoblasts of Acystosporidae, 104 f.
Zygotomeres (= naked spores of Acystosporidae), 104 f.
Zygotonucleus (= Fusion-nucleus, a nucleus formed by fusion of two
gametonuclei), 33 f.
Zygotospore (= resting zygote), 97
Zykoff, 178
Zymase (= chemical ferment), 15;
in relation to brood-division, 32 f.

END OF VOL. I

_Printed by_ R. & R. CLARK, LIMITED, _Edinburgh_.

[1] For detailed studies of protoplasm see Delage, _Hérédité_, 2nd ed.
1903; Henneguy, _Leçons sur la Cellule_, 1896; Verworn, _General
Physiology_, English ed. 1899; Wilson, _The Cell in Development and
Inheritance_, 2nd ed. 1900. All these books contain full
bibliographies.

[2] As we shall see later, it is by no means easy to separate sharply
Protozoa and Protophyta, the lowest animals and the lowest plants;
and therefore in our preliminary survey to designate lowly forms of
life, not formed of the aggregation of differentiated cells, we shall
employ the useful term "Protista," introduced by Haeckel to designate
such beings at large, without reference to this difficult problem of
separation into animals and plants (see also p. 35 f.).

[3] The "micron," represented by the Greek letter µ, is 1/1000 mm., very
nearly 1/25,000 of an inch, and is the unit of length commonly
adopted for microscopic measurements.

[4] A solid substratum is required, to which the lower surface adheres
slightly: that movement is complicated by a sort of rolling over of
the upper surface, constantly prolonging the front of the
pseudopodium, while the material of the lower surface is brought up
behind. H. S. Jennings, _Contr. to the Study and Behaviour of the
Lower Organisms_, 1904, pt. vi. p. 129 f., "The Movements and
Reactions of Amoeba."

[5] If the protoplasm contains visible granules, as it usually does,
within a clear external layer, we see that these stream constantly
forwards along the central axis of each process as it forms, and
backwards just within the clear layer all round, like a fountain
playing in a bell-jar. This motion is most marked when a new
pseudopodium is put forth, and ceases when it has attained full
dimensions.

[6] We use as a corresponding adjective the term "plasmic."

[7] For the study of the structure of protoplasm under the microscope it
is necessary to examine it in very thin layers, such as can for the
most part be obtained only by mechanical methods (section-cutting,
etc.). These methods, again, can only be applied to fixed specimens,
for natural death is followed by rapid changes, and notably by
softening, which makes the tissue less suitable for our methods. We
further bring out and make obvious pre-existing differentiations of
our specimens by various methods of staining with such dyes as
logwood and cochineal and their derivatives, and coal-tar pigments
(see also p. 11 n.).

[8] In many Protista these granules have been shown by Schewiakoff, in
_Z. wiss. Zool._ lvii. 1893, p. 32, to consist of a calcium
phosphate, probably Ca_{3}P_{2}O_{8}.

[9] It is not always possible to tell how much of these structures
represents what existed in life (see p. 11).

[10] The chromatin and nucleoles are especially rich in phosphorus,
probably in the combination nucleinic acid.

[11] In chemical phrase the process is "exothermic."

[12] The growth of crystals is a mere superficial deposit, and cannot at
all be identified with protoplasmic growth.

[13] A. Bolles Lee, in his _Microtomist's Vade Mecum_, 1st ed. (1885),
pointed out that "Clearing reagents are liquids whose primary
function is to make microscopic preparations transparent by
penetrating amongst the highly refractive elements of which the
tissues are composed, having an index of refraction not greatly
inferior to that of the tissues to be cleared" (p. 213). We showed
later ("The State in which Water exists in Live Protoplasm," in _Rep.
Brit. Ass._ 1889, p. 645, and _Journ. Roy. Micr. Soc._ 1890, p. 441)
that since the refractivity of living protoplasm is only 1.363-1.368,
it follows that the water in the living protoplasm is in a state of
perfect physical combination, like the water of a solution of gum
[read a "mucilage"] or of a jelly. Now the phenomena of protoplasmic
motions as studied in the Rhizopoda and in the vegetable cell, seem
absolutely to preclude the jelly supposition, and for these cases we
must admit that living protoplasm is a viscid liquid whose
refractivity is probably the mean of the two constituents separated
by death, the one solid, the other a watery solution: and death is
for us essentially a process of precipitation (or better,
"desolution"). For further work on these lines see Hardy in _Journ.
Physiol._ vol. xxiv. 1899, p. 158, and Fischer, _Fixirung u.
Färbung_, 1900.

[14] In its original use "automatism" designates the continuous sequence
and combination of actions, without external interference, performed
by complex machines designed and made for specific ends by
intelligent beings: thus we speak correctly of "automatic ball
bearings" that tighten of themselves when they become loose; but even
these cannot take up fresh steel and redeposit it, either to replace
the worn parts or to strengthen a tube that is bending under a
stress.

[15] Proteids are organic compounds containing carbon, hydrogen, nitrogen,
and oxygen, of which white of egg (albumen) is a familiar type.
Nucleo-proteids are compounds of proteids with nucleinic acid, which
in addition to the above elements contain phosphorus.

[16] The specific gravity of living protoplasm has been estimated by
determining the density of a solution of gum in which certain
Infusoria float freely at any depth. It was found by the concurrent
results of Julia B. Platt and Stephen R. Williams (see _Amer.
Natural._ xxxiii. 1899, p. 31, xxxiv. 1900, p. 95) to be from 1.014
to 1.019, while the Metazoon _Hydra_ was found to give a density of
only 1.0095 to 1.0115. The difference of about 0.006, it is easy to
show, is of the correct "order of magnitude," if we admit that the
actual substance of the Hydra has about the same specific gravity as
the Infusorian, while the density of the whole is lightened by the
watery contents of the internal cavity, etc. Jensen obtained a much
higher result for _Paramecium_, using a solution of the crystalloid
substance, potassium carbonate; but it is almost certain that this
would be readily absorbed by the organism, and so raise its density
in the course of the experiment.

[17] Energy may be derived from the mere _splitting up_ of complex
substances within the cell: when such a splitting involves the
liberation of CO_{2} the process is (mis-)called "intramolecular
respiration."

[18] A similar organ, but with _cellular_ walls, is the bladder of the
Rotifers and certain Platyhelminthes, in connexion with their renal
system (vol. ii. pp. 53, 199, and especially pp. 213-5).

[19] In _Rep. Brit. Ass._ 1888, p. 714; _Ann. Mag. Nat. Hist._ (6), iii.
1889, p. 64. This view has been fully worked out, mainly on Ciliates,
by Degen in _Bot. Zeit._ lxiii. Abt. 1. 1905.

[20] See Hartog, "On Multiple Cell-division, as compared with Bi-partition
as Herbert Spencer's limit of growth," in _Rep. Brit. Ass._ 1896, p.
833; "On a Peptic Zymase in Young Embryos," _ibid._ 1900, p. 786;
"Some Problems of Reproduction," ii. _Quart. Journ. Micr. Sci._
xlvii. 1904, p. 583.

[21] "On the Digestive Ferment of a large Protozoon." _Rep. Brit. Ass._
1893, p. 801.

[22] See for studies of the movements of Protoplasm, Berthold,
_Protoplasmamechanik_ (1886); Bütschli, _Investigations on
Microscopic Foams and on Protoplasm_, English ed. 1894; Verworn,
_General Physiology_, 1899; Le Dantec, _La Matière Vivante_, 1893?;
and Jensen, "Unters. ueb. Protoplasmamechanik," in _Arch. Ges. Phys._
lxxxvii. 1901, p. 361; Davenport, _Experimental Morphology_, i. 1897;
H. S. Jennings, _Contr._ etc. 1904.

[23] The terms "expansion" and "contraction" refer only to the
_superficial area_: it is very doubtful whether the _volume_ alters
during these changes.

[24] For discussions on the mechanism of ciliary action, see Schäfer,
_Anat. Anz._ xxiv. 1904, p. 497, xxvi. 1905, p. 517; Schuberg, _Arch.
Protist._ vi. 1905, p. 85.

[25] Like the line of most rapid growth in a circumnutating plant-stem.

[26] A similar body lies at the centre to which the axial filaments of the
radiating pseudopodia of the Heliozoa converge, and might be termed
by parity a "podoplast"; but "centrosome" is a convenient general
term to include all such bodies. It is clearly of nuclear origin in
_Trypanosoma_ (Fig. 39, p. 120).

[27] See for development of this view W. M'Dougall in _Journ. Anal.
Physiol._ xxxi. 1897, pp. 410, 539. I put it forward in the first
draft of this essay in 1894.

[28] The best general account is to be found in Davenport, _Experimental
Morphology_, 1897.

[29] See Jennings in _Woods Holl. Biol. Lect._ 1899, p. 93.

[30] It is not always easy to distinguish these two classes of phenomena.

[31] Jennings, in his studies on _Reactions to Stimuli in Unicellular
Organisms_ (1899-1900), has shown that whatever be the nature of the
repellent stimulus, chemical or mechanical or thermal, the reaction
of _Paramecium_ and many other Protista is always the same. It swims
backward a short distance, turns towards the aboral surface, and then
having thus reversed swims on again in the new direction, front
foremost as before. Apparent "positive taxies" are often really
negative ones; for if the _Paramecium_ be placed in water containing
CO_{2} it shows the reaction not on entering the part charged with
this acid, but on passing away from it into purer water, so that it
continually tends to turn back into the acid part, while within it or
in the water at a distance not yet charged it swims about
irregularly. It appears due to this that the individuals become
aggregated together, as they excrete this gas into the water. If a
repellent substance diffuse towards the hinder end of a _Paramecium_,
the response, instead of carrying it away, brings it into the region
of greater concentration, and may thus kill it.

[32] "Galvanotaxis and Chemotaxis," _Journ. of Physiol._ vol. xxvi.
1900-1901, p. 291.

[33] Let us take the case of a 1-centimetre cube, growing to the size of a
2-centimetre cube. The superficial area of the 1 cm. cube measures 6
square centimetres, and its bulk is 1 cubic centimetre. The
superficial area of the 2-centimetre cube measures 24 square
centimetres, while its volume measures 8 cubic centimetres. Thus the
larger cube has only 3 cm. sq. of surface to every cubic cm. of
volume, instead of 6; in other words, the ratio of surface to volume
has been halved by growth. Three successive bipartitions of the
larger cube will divide it into eight separate 1-centimetre cubes,
each now possessing the original ratio of surface to volume.

[34] The nucleus is regarded by some as equivalent to a central nervous
organ for the cell; by others, such as G. Mann and Verworn, as the
chief chemical centre of the cell, and notably the seat of the
secretion of the zymases or ferments that play so important a part in
its life-work; for it is found that a Protist deprived of its nucleus
can execute its wonted movements, but can neither digest nor grow.
This conclusion may appear to be rather sweeping and premature, but
we have seen that the changes of surface tension are the direct
antecedents of the motions of the cytoplasm, we know that such
changes are induced by chemical changes; and thus the nucleus—if it
be the central laboratory to which such changes are ultimately
due—would really in a certain sense be a directive centre.

[35] The term "resting" is very ill-chosen, for even superficial
observation shows that the relative position and characters of the
internal structures of such a nucleus are constantly changing with
the vital activities and functions of the cell.

[36] For a detailed study of the nucleus in Protista, see Calkins in
_Arch. Protistenk._ vol. ii. 1903.

[37] The "centriole" is a minute granule sometimes recognisable in the
centre of the centrosphere, and undergoing fission in advance. But
centrosomes are often found without a distinction into centrosphere
and centriole, and there is much confusion in the use of the terms.

[38] The origin of the centrosomes is a problem not yet certainly solved,
if indeed it be susceptible of any universal solution. They are
certainly absent in many plants; and, on the other hand, structures
which correspond to them often appear in mitotic divisions of
Protista. In some cases the centrosomes are undoubtedly of nuclear
origin, and pass out through the nuclear wall into the cytoplasm.

[39] Though the forces at work in the dividing cell are similar in their
effects to such physical forces as magnetism, static electricity, and
even capillarity, and models utilising such physical forces have been
devised to represent the strain-figures of the cell, the cell forces
are distinct from any known physical force. For discussions of the
nature of the forces at work, with bibliographies, see Angel
Gallardo, _Interpretatión Dinámica de la División Celular_, 1902;
Rhumbler, in _Arch. Entw._ xvi. 1903, p. 476; Hartog, _C.R._
cxxxviii. 1904, p. 1525, and "On the Dual Force of the
Dividing-cell," pt. i. _Proc. Roy. Soc._ 1905 B, lxxvi. p. 548.

[40] See Th. Boveri, _Ergebnisse ueb. d. Konstitution d. chromatischen
Substanz des Zellkerns_ (1903), for the most recent defence of this
view. He lays, however (p. 2), far more stress on the individuality
of the segments themselves than on the actual chromatin material they
contain.

[41] The fact that it is by mitotic division that the undifferentiated
germ-cells produce the "differentiated" tissue-cells of the body of
the highest animals, is again irreconcilable with such theories,
whose chief advocates have been A. Weismann and his disciples.

[42] Temporary plastogamy is a process found in some Foraminifera, where
two organisms unite by their cytoplasms so that there can be complete
blending of these, while the nuclei remain distinct: they ultimately
separate again. In the conjugation of the Infusoria, the union of the
cytoplasms is a temporary plastogamy (see p. 148 f.).

[43] See Figs. 9, 29, 31, 34, etc., pp. 54, 89, 95, 101.

[44] One obvious effect of brood-formation is to augment rapidly the ratio
of superficial area to bulk: after only three divisions (p. 23, note)
the ratio is doubled; if the divisions be nine in succession so as to
produce a brood of 512, the ratio is increased eightfold, on the
supposition that the figure is preserved. However, the
brood-mother-cell is usually spherical, while zoospores are mostly
elongated, thus giving an additional increase to the surface, which
we may correlate with that increased activity; so that they
disseminate the species, spreading far and wide, and justifying the
name of "spore" in its primitive sense (from the Greek σπείρω—I
scatter [seed]).

[45] This condition may be protracted in the segmentation of the egg of
certain Higher Animals, such as _Peripatus_ (Vol. V. p. 20). It is
clearly only a secondary and derived condition.

[46] The usual antecedent of change in the condition of the egg is
"fertilisation"—its conjugation with the sperm; but this is not
invariable; and a transitory sojourn of certain marine eggs in a
liquid containing other substances than sea-water may induce the egg
on its return to its native habitat to segment and develop. This has
been mistermed "Chemical fertilisation," discovered within the last
six years by Jacques Loeb, and already the subject of an enormous
literature.

[47] See Hartog in _Rep. Brit. Ass._ 1896, p. 933, 1900, p. 786.

[48] Commonly called "fertilisation," or "sexual union," inadequate and
misleading terms.

[49] For details see Hartog, "Some Problems of Reproduction," _Quart.
Journ. Micr. Sci._ xxxiii. p. 1, xlvii. p. 583; and _Ann. Biol._ vol.
iv. (1895) 1897; E. B. Wilson, Yves Delage, and Henneguy (references
on p. 3, note); and for a singularly clear and full treatment of the
processes in Protozoa, Arnold Lang, _Lehrb. d. Vergl. Anat._ 2nd ed.
Lief. 2, "Protozoa," 1900.

[50] This phenomenon, which we have termed "exogamy," is common in
Protophyta; it has been clearly demonstrated by Schaudinn in
Foraminifera and the Lobose Rhizopod _Trichosphaerium_ (p. 53 f. Fig.
9), and by Pringsheim in the Volvocine _Pandorina_ (p. 128 f. Fig.
45). It is quite independent of the differentiation of _binary_ sex.

[51] Other modes of syngamy, such as karyogamy and plastogamy, we shall
discuss below, pp. 69, 148; see also p. 30.

[52] See Gruber in _Biol. Centralb._ iv. p. 710, v. p. 137 (1884-6), in
_Ber. Ges. Freiburg_, i. ii. 1886-7; Verworn (reference on p. 16); F.
R. Lillie in _Journ. Morph._ xii. 1896, p. 239; Nussbaum in _Arch.
mikr. Anat._ xxvi. 1886, p. 485; Balbiani in _Recueil Zool. Suisse_,
v. 1888, in _Zool. Anz._ 1891, pp. 312, 323, in _Arch. Microgr._ iv.
v. 1892-3. For Higher Organisms especially see T. H. Morgan,
_Regeneration_, 1901.

[53] Whence the antiseptic powers of such aromatic alcohols as phenol and
thymol, and acids as salicylic acid, etc., and their salts and
esters.

[54] The portion of the spectrum that is operative in "holophytic"
nutrition is the red or less refrangible half, and notably those rays
in the true red, which are absorbed by the green pigment chlorophyll,
and so give a dark band in the red of its absorption spectrum. The
more refrangible half of the spectrum, so active on silver salts,
that it is usually said to consist of "chemical rays," is not only
inoperative, but has a destructive action on the pigments themselves,
and even on the protoplasm. Chlorophyll is present in all cases even
when more or less modified or masked by the accompaniment of other
pigments.

[55] Similarly, threads unite the cells of the colonial plant—Flagellate
_Volvox_, passing through the thick gelatinous cell-wall (pp.
126-127, Fig. 44).

[56] Pigments soluble in the ordinary solvents of fats, such as ether,
benzol, chloroform, etc.

[57] We have ourselves had hard work to persuade intelligent men of fair
general education, even belonging to a learned profession, that this
is not the case.

[58] Dr. H. Charlton Bastian has recently maintained a contrary thesis
(_The Nature and Origin of Living Matter_, 1905), but has adduced no
evidence likely to convince any one familiar with the continuous
life-study of the lower organisms.

[59] The terms "organoid," "organella," have been introduced to designate
a definite portion of a Protist specialised for a definite function;
the term "organ" being reserved for a similarly specialised group of
cells or tissues in a Metazoon or Metaphyte. We do not consider that
this distinction warrants the introduction of new words into the
terminology of general Zoology, however convenient these may be in an
essay on the particular question involved.

[60] This has been especially the case with the Flagellata, the
Proteomyxa, and the Mycetozoa.

[61] Lang distinguishes "lobopodia," "filopodia," and "pseudopodia"
according to their form,—blunt, thread-like, or anastomosing. In some
cases the protoplasm shows a gliding motion as a whole without any
distinct pseudopodium, as in _Amoeba limax_ (Fig. 1, p. 5), and a
pseudopodium may pass into a thin, active flagellum, which is,
however, glutinous and serves for the capture of prey: such often
occurs in the Lobosa _Podostoma_ and _Arcuothrix_, which are possibly
two names for one species or at least one genus; and in many cases a
slender pseudopodium may be waved freely.

[62] See Schewiakoff, "Ueb. d. Geograph. Verbreitung d.
Süsswasserprotozoen," in _Mém. Acad. St. Pétersb._ ser. 7, xli. 1893,
No. 8. His views apply to most minute aquatic organisms—Animal,
Vegetable, or Protistic.

[63] See E. R. Lankester, art. "Protozoa" in _Encycl. Brit._ 9th ed.
(1885), reprinted with additions in "Zoological Articles." We cannot
accept his primary division into Corticata and Gymnomyxa, which would
split up the Flagellata and mark off the Gregarines from the other
Sporozoa.

[64] On this ground I have referred _Paramoeba_, Greeff, to the
Cryptomonadineae.

[65] Differences (1) from _Foraminifera_; (2) from _Heliozoa_; (3) from
_Proteomyxa_ and _Sporozoa_; (4) from _Myxomycetes_; (5) from many
_Foraminifera_.

[66] I have not followed the usual classification into Gymnamoebae and
Thecamoebae, according to the absence or presence of a test
(perforated by one or more openings) in the active state, as such a
test occurs in isolated genera of Flagellata and Infusoria, and does
not appear to have any great systematic importance.

[67] The significance of chromidia in Sarcodina (first noted by Schaudinn
in Foraminifera) was fully recognised and generalised by R. Hertwig
in _Arch. Protist._ i. 1902, p. 1.

[68] Stolč in _Z. wiss. Zool._ lxviii. 1900, p. 625. Lilian Veley,
however, gives reasons for regarding them as of proteid composition,
_J. Linn. Soc._ (_Zool._) xxix. 1905, p. 374 f. They disappear when
the _Pelomyxa_ is starved or supplied with only proteid food.

[69] This genus contains two sausage-shaped, blueish-green plastids,
possibly symbiotic Cyanophyceous Algae.

[70] See Lauterborn in _Z. wiss. Zool._ lix. 1895, pp. 167, 537.

[71] C. Scheel has seen _Amoeba proteus_ produce a brood of 500-600 young
amoebulae, which he reared to full size (in _Festschr. f. Kupffer_,
1899).

[72] _Arb. Kais. Gesundheitsamte Berlin_, xix. 1903.

[73] _Faune Rhizopodique du Bassin du Léman_, 1902. See also Cash, _The
British Freshwater Rhizopoda and Heliozoa_, vol. i., Ray Society,
1905.

[74] Chapman, _The Foraminifera_, London, 1902; Lister, "Foraminifera" in
Lankester's _Treatise on Zoology_, pt. i. fasc. 2, 1903.

[75] _Challenger Reports_ (_Zool_.), vol. ix. 1884.

[76] In Lankester's _Treat. Zool._ pt. i. fasc. 1. For other
classifications see Eimer and Fickert in _Z. wiss. Zool._ lxv. 1899;
Rhumbler in Lang's _Protozoa_, 1901; and for a full synopsis of
genera and species, "Systematische Zusammenstellung der recenten
Reticulosae" (pt. i. only), in _Arch. Prot._ iii. 1903-4, p. 181.

[77] The type of Dujardin's genus _Gromia_ is _G. oviformis_ = _Hyalopus
dujardinii_, M. Sch., which is one of the Filosa.

[78] This convenient name is due to my friend Dr. A. Kemna of Antwerp.

[79] The name Foraminifera was used to express the fact that the chambers
communicated by pores, not by a tubular siphon as in Nautiloidea and
Ammonoidea (Vol. III. pp. 393, 396).

[80] Which probably accounts for the earlier failure of Lister and of
Schaudinn himself to note their conjugation.

[81] Rhumbler, "Die Doppelschalen v. _Orbitolites_ u. and. Foraminiferen,"
in _Arch. Protist._ i. 1902, p. 193.

[82] The alleged Archaean genus _Eozoon_, founded by Carpenter and Dawson
on structures found in the Lower Laurentian serpentines
(ophicalcites), and referred to the close proximity of Nummulites,
has been claimed as of purely mineral structure by the petrologists;
and recent biologists have admitted this claim.

[83] Possibly composed of the same proteid, "acanthin," that forms
spicules of greater permanence in the Acantharia among the Radiolaria
(p. 75 f. Figs. 24, 25, A).

[84] Such divisions into functional and abortive sister nuclei are termed
"reducing divisions," and are not infrequent in the formation of
pairing-cells, especially oospheres of Metazoa, where the process is
termed the maturation of the ovum.

[85] Besides these genera enumerated by Schaudinn, we include _Dimorpha_
Gruber (Fig. 37 5, p. 112), _Mastigophrys_ Frenzel, _Ciliophrys_
Cienk., and _Actinomonas_ usually referred to Flagellates.

[86] K. Brandt, in _Arch. Prot._ i. 1902, p. 59, regards the presence of
spicules as not even of generic moment, and subdivides the Collodaria
into two families—_Collida_ (solitary), and _Sphaerozoea_, colonial,
_i.e._ with numerous central capsules.

[87] Dreyer adds an additional order—Sphaeropylida, distinguished by a
basal (or a basal and an apical) pylome.

[88] Verworn has shown that _Thalassicolla nucleata_ can, when the
exoplasm is removed from the central capsule, regenerate it
completely. First a delicate exoplasm gives off numerous fine
radiating pseudopodia, and the jelly is re-formed at their bases, and
carries them farther out from the central capsule. See _General
Physiology_ (Engl. ed. 1899), p. 379.

[89] The pigment is singularly resistant and insoluble, and shows no
proteid reaction. Borgert states that it appears to be formed in the
oral part of the endoplasm, and to pass through the astropyle into
the ectoplasm, where it accumulates. It is probably a product of
excretion, and may serve, by its retention, indirectly to augment the
surface. See Borgert, "Ueb. die Fortpflanzung der tripyleen
Radiolarien" in _Zool. Jahrb. Anat._ xiv. 1900, p. 203.

[90] Dreyer has shown that in many cases it may be explained by
geometrical considerations. V. Häcker has written a most valuable
account of the Biological relations of the skeleton of Radiolaria in
_Jen. Zeitschr._ xxxix. 1904, p. 297.

[91] _Zool. Jahrb. Anat._ xiv. 1900, p. 203.

[92] Porta has described reproduction by spores and by budding in
Acantharia, _Rend. R. Ist. Lomb._ xxxiv. 1901 (ex _Journ. R. Micr.
Soc._ 1903, p. 45). In _Thalassophysa_ and its allies zoospore
reproduction appears to be replaced by a process in which the central
capsule loses its membrane, elongates, becomes multinuclear, and
ultimately breaks up into the nucleate portions, each annexing an
envelope of ectoplasm to become a new individual (see _Arch. Prot._
vol. i. 1902).

[93] Brandt, "Die Koloniebildenden Radiolarien," in _Fauna u. Flora des
Golfes v. Neapel_, xiii. 1885, gives a full account of the
Zooxanthellae and Diatoms, and notes the parasitism of _Hyperia_.

[94] See Köppen in _Zool. Anz._ xvii. 1894, p. 417. For _Sticholonche_,
see R. Hertwig in _Jena. Zeitsch._ xi. 1877, p. 324; and Korotneff in
_Zeitsch. wiss. Zool._ li. 1891, p. 613. Borgert's paper on
Dictyochidae is in the same volume, p. 629.

[95] Most of Haeckel's Monera, described as non-nucleate, belong here.
Several have been proved to be nucleate, and to be rightly placed
here; and all require renewed study.

[96] Even the Acystosporidiae have sickle-germs (blasts) in the insect
host.

[97] See Zopf, _Beitr. Nied. Org._ ii. 1892, p. 36, iv. 1894, p. 60, for
the doubtful genus _Chlamydomyxa_; Hieronymus, abstracted by
Jenkinson, in _Quart. J. Micr. Sci._ xiii. 1899; Penard, _Arch.
Protist._ iv. 1904, p. 296.

[98] The name "aethalium" is now always used in this sense.

[99] The group was monographed by Schröter in Engler and Prantl's
_Pflanzenfamilien_, I. Teil, Abt. 1, 1897. See also A. Lister's
Monograph of the Mycetozoa, 1894; Massee, Monog. of the Myxogastres,
1893; Sir Edward and Agnes Fry, _The Mycetozoa_, 1899; and Massee
MacBride, _The North American Slime Moulds_, 1899.

[100] Several monographs of the group have been published recently dealing
with the group from a systematic point of view, including their
relation to their hosts. Wasielewski, "Sporozoenkunde" (1896); Labbé,
"Sporozoa" (in _Tierreich_, 1899). Doflein's "Protozoen als Parasiten
und Krankheitserreger" (1901) contains most valuable information of
the diseases produced by these and other Protozoic hosts. Minchin's
Monograph in Lankester's _Treatise on Zoology_, pt. i. fasc. 2
(1903), is a full account of the class, and admirable in every way.

[101] For its reactions see Bütschli, _Arch. Protist._ vii. 1906, p. 197.

[102] The cuticle in the allied genus _Lankesteria_, which is the form we
figure on p. 95, is perforated by a terminal pore, through which the
clear plasma of the sarcocyte may protrude as a pseudopodium.

[103] This account is taken from Cuénot (in _Arch. de Biol._ 1900, p. 49),
which confirms Siedlecki's account of the process in the allied genus
_Lankesteria_ in _Bull. Acad. Cracow_, 1899. Wolters's previous
description, assimilating the processes to those of _Actinophrys_, is
by these authors explained as the result of imperfect preservation of
his material.

[104] See p. 120.

[105] See Caullery and Mesnil, "Rech. sur les Actinomyxidies," _Arch. Bot._
vi. 1905, p. 272 f.

[106] Léger, _Arch. Zool. Exp._ sér. 3, x. and sér. 4, v. (1902-3); for a
full discussion of the relations of association and conjugation in
Gregarines, see Woodcock in _Quart. Journ. Micr. Sci._ l. 1906, p. 61
f.

[107] A _Lithobius_ is figured in Vol. V. p. 45.

[108] The schizont forms of some species, before the invariable alternation
of schizogony and sporogony had been made out clearly, were regarded
as "monogenic" genera, under the names of _Eimeria_, A. Schn., and
_Pfeifferella_, Labbé; while those in which the formation of spores
containing sickles had been clearly seen were termed "digenic."
Labbé's monograph, "Die Sporozoen," in the _Tierreich_, is
unfortunately written from this point of view, which had already
become doubtful, and is now demonstrated to be erroneous, chiefly by
the labours of Schaudinn and Siedlecki.

[109] A species has been described, however, in the blood of the Indian
Gerbille (_Gerbillus indicus_), completing the sexual process in the
Louse of its host. A figure of _G. aegyptius_ will be found in Vol.
X. (1902) p. 475.

[110] There is no difference between a mosquito (little fly) and a gnat,
both names are applied indiscriminately to thin-bodied Diptera of the
group Nemocera which attack man; only the females bite (see Vol. VI.
pp. 466-468).

[111] Regarded by Schaudinn as a state of the Flagellate _Trypanosoma_ (p.
119 f.).

[112] In _Quart. Journ. Micr. Sci._ xliv. 1901, p. 429.

[113] It would seem that resting-cells, _i.e._ the crescents and
corresponding spheres, of _Laverania_ and _Haemamoeba_ may linger
during months of apparent health in the spleen and red marrow of the
bones; and that these by parthenogenesis produce sporozoites and
determine relapses when, owing to a lowering of the general health,
conditions favourable to new sporulation occur.

[114] Léger and Duboscq have found that _Sarcocystis tenella_, a parasite
common in the muscles of the sheep (and rarely found in man), has a
conjugation and sexual process recalling that of _Stylorhynchus_,
save that the sperms are much smaller than the ova (_C.R._ 1902, i.
p. 1148).

[115] The alleged micronucleus of certain forms appears to be merely a
"blepharoplast" (see p. 19); even when of nuclear origin, as in
_Trypanosoma_, it has no function in reproduction like the
micronucleus of Infusoria (see pp. 115, 120 f.).

[116] _Dimorpha_ is now referred to Heliozoa (p. 70).

[117] _I.e._ resembling the thread-like water Algae.

[118] Trichocysts (see p. 142) occur in some Chloromonadaceae; and the
Dinoflagellate _Polykrikos_ possesses true nematocysts (see p. 131).

[119] For a full monograph of this family see H. Lohmann, in _Arch. f.
Protistenkunde_, vol. i. 1902, p. 89.

[120] Delage has well explained the action of the single anterior flagellum
which waves in a continuous spiral like a loaded string whirled round
one's head; it thus induces a movement of the water, beyond its
actual range, backwards and outwards, maintained by a constant influx
from behind, which carries the cell onward at the same time that it
necessarily rotates round its axis. If there is a pair of
symmetrically placed flagella they co-operate like the arms of a
swimmer; when the second flagellum is unilateral the motion is most
erratic, as seen in the Bodonidae (and the zoospores of many
Chytridieae, which have most of the characters of the Flagellates,
though habitually removed to the Fungi).

[121] The colouring matter is chlorophyll or some allied colouring matter.
In the yellow and brown forms the additional pigment is termed
loosely "diatomin," but its identity with that of Diatoms is in no
case proved.

[122] Notably in the Craspedomonadidae, where transverse division also
occurs. See Raoul Francé, _Die Craspedomonadineen_ (Buda-Pesth,
1897).

[123] And also in the "Monads," described by Dallinger and Drysdale, see
above.

[124] In _Cercomonas dujardinii_, _Polytoma uvella_, and _Tetramitus
rostratus_ the gametes resemble the ordinary forms and are isogamous.
In _Monas dallingeri_ and _Bodo caudatus_ conjugation takes place
between one of the ordinary form and size and another similar but
smaller. In _Dallingeria drysdali_ the one has the ordinary size and
form, the other is equal in size, but has only one flagellum, not
three; in _Bodo saltans_ they are unequal, the larger gamete arising
in the ordinary way by longitudinal fission, the smaller by
transverse division. Doubt has been thrown on the validity of our
authors' results by subsequent observers abroad; but I can find no
evidence that these have even attempted to repeat the English
observations under the same severely critical conditions, and
therefore consider the attacks so far unjustified. Schaudinn has
observed conjugation between _Trichomonas_ individuals which have
lost their flagella and become amoeboid; also in _Lamblia
intestinalis_ and in _Trypanosoma_ (_Halteridium_?) _noctuae_ (Fig.
39) "Reduction-divisions" (see p. 75, note 1) of the nuclei take
place before fusion, and the nuclear phenomena are described as
"complicated" (_Arb. Kais. Gesundheitsamte_, xx. 1904, p. 387).
_Paramoeba eilhardii_ in its adult state is colourless, amoeboid,
multiciliate. It forms a brood cyst, from which are liberated
flagellate zoospores, with a chromatophore, which reproduce by
longitudinal fission in this state. They may also conjugate.

[125] In _P.R.S._ xxvii. 1878, p. 332.

[126] In _Z. wiss. Zool._ lv. 1893, p. 353.

[127] 1. Teil, Abt. 1. a, 1900.

[128] In the _Chlorophyceae_, 1. Teil, Abt. 2, 1897.

[129] 1. Teil, Abt. 1. b, 1896.

[130] Besides the above, Dangeard, in various papers in his periodical _Le
Botaniste_, has treated of most of the groups, and Raoul Francé has
monographed the _Polytomeae_ in the _Jahrb. wiss. Bot._ xxvi. 1894,
p. 295, and Dill the genus _Chlamydomonas_, etc., its closest allies,
in _op. cit._ xxviii. 1895, p. 323.

[131] For a detailed abstract of our knowledge of _Trypanosoma_ and its
allies up to Feb. 1, 1906, see Woodcock, "The Haemoflagellates," in
_Quart. Journ. Micr. Sci._ 1. 1906, p. 151.

[132] Doubts still subsist as to the interpretation of Schaudinn's
observations.

[133] _Quart. Journ. Micr. Sci._ xlvi. 1902.

[134] A Zambezian Tick infects man with a _Treponema_, producing
relapsing-fever; another species is found in the tropical disease
"framboesia" ("yaws" or "parangi").

[135] Stated by Geza Entz and Raoul Francé to be due to the spiral twisting
of a plasmic membrane, and to be like a cone formed by twisting
paper, with the free edges overlapping.

[136] Discovered by Leidy. For the most recent description of this group
see Grassi and Sandias in _Quart. Journ. Micr. Sci._ xxxix. (figures)
and xl. p. 1 (text), 1897.

[137] Bezzenberger has given an analytical table of the eleven known
species of the genus _Opalina_ in _Arch. Protist._ iii. 1903, p. 138.

[138] Such movements, permissible by the perfectly flexible but firm
pellicle, are termed "metabolic" or "euglenoid" in contradistinction
to "amoeboid." They also occur in many Sporozoa.

[139] Within which is often harboured the Rotifer, _Proales parasita_, Vol.
II. p. 227.

[140] In the Adinidae there is no groove; the two lashes arise close
together, and the one is coiled round the base of the other.

[141] In _Unt. Inst. Tübingen_, i. 1883, p. 233.

[142] Conjugation of adults has been observed by Zederbauer (_Ber. Deutsch.
Ges._ xxii. 1904). A short connecting tube is formed by the meeting
of outgrowths from either mate; their protoplasmic contents meet and
fuse herein to form a spherical resting-spore, as in the Conjugate
Algae.

[143] According to Bergh, _Polykrikos_ has as many nuclei as grooves, each
accompanied by one or more "micronuclei." Possibly these latter
bodies are merely blepharoplasts, in connexion with the transverse
flagella.

[144] Engler and Prantl's _Pflanzenfamilien_, 1. Teil, Abt. 1, 1896.

[145] The luminous genus, _Pyrocystis_ (Fig. 47), regarded as a
Cystoflagellate by Wyville Thomson, has a cellulose wall, no mouth,
and in the zoospore state has the two flagella in longitudinal and
transverse grooves of the Dinoflagellata.

[146] This process has the character of telolecithal segmentation in a
Metazoan egg.

[147] See Doflein, in _Zool. Jahrb. Anat._ xiv. 1900, p. 1.

[148] London, 1753, 402-403.

[149] On this account Hickson has termed the group "Heterokaryota" in
Lankester's _Treat. Zool._ i. fasc. 1, 1903.

[150] See Baker, _Employment for the Microscope_, ed. 2, 1758.

[151] Saville Kent's valuable _Manual of the Infusoria_ (1880-1882), which
gives figures of every genus and descriptions of every species known
at that date, includes the Flagellates in its scope.

[152] Orders 1 and 2 constitute together the _Holotricha_ of Stein;
Bütschli regards 3 to 6 as sections of _Spirotrocha_.

[153] Dextrorse in all but _Lichnophora_ and _Spirochona_.

[154] Each membranella is a transversely elongated oval in reality, and
below it is a double row of basal granules, corresponding to the
individual cilia that constitute it. Similarly, the undulating
membranes have a single row of basal granules.

[155] Tail-like appendages are found in _Scaphiodon_ and in _Dysteria_ and
its allies (Gymnostomaceae), _Urocentrum_ (Aspirotrichaceae),
_Discomorpha_ and _Caenomorpha_ (Heterotrichaceae). In the first two
and last two cases they are prolongations of the body; in the third
an aggregate of cilia. One or more long caudal setiform cilia are
present in the genera _Lembadion_, _Pleuronema_, _Cyclidium_,
_Lembus_, _Cinetochilum_, _Ancistrum_, and _Uronema_; all these are
addicted to making springing darts. Tufts of cilia of exceptional
character often serve for temporary attachment. The stalk (or at
least its external tube) of the Peritrichaceae appears to be the
chitinous excretion of a zone of such cilia. Fauré-Fremiet terms such
a zone or annular brush a "scopula" ("Struct. de l'app. fixateur chez
les Vorticellides," _Arch. Protist._ vi. 1905, p. 207). For a
discussion of the finer structure of the cilia in Ciliata, and the
mechanism of their action, see Schuberg, _Arch. Protist._ vi. 1905,
p. 61.

[156] See Mitrophanow "Sur les Trichocystes ... du _Paramoecium_," _Arch.
Protist._ v. 1904, p. 78.

[157] The "neurophane" fibrils of Neresheimer, _Arch. Protist._ ii. 1903,
p. 305 f.

[158] Sometimes the number of afferent canals is limited to five
(_Paramecium_), or even one. There may be one or more contractile
vacuoles, and in the latter case the different ones have an
independent rhythm.

[159] It is from such conclusive cases that the universal character of a
discharge to the surface has been inferred in the rest of Protista
possessing this organ.

[160] _Gruber_ (_Ber. Ges. Freib._ 1888) has shown that in several marine
Ciliata the meganucleus is represented by an enormous number of
minute granules disseminated through the endosarc, which, on the
approach of fission, unite into a single meganucleus. As an adjacent
micronucleus makes its appearance at this stage, he infers that the
micronucleus must be also resolved in the intermediate life of the
cell into granules too small for recognition under the highest
magnification attainable, and that they must then coalesce.

[161] In the peculiar Peritrichan _Spirochona_ the division of the
meganucleus is a much more complex process than usual, and recalls
that of the undifferentiated nuclei of many Rhizopods (see Rompel in
_Z. wiss. Zool._ lviii. 1894, p. 618). _Opalina_ has neither mouth
nor anus, nor contractile vacuole, but a large number of similar
nuclei, that divide by a true mitotic process, like micronuclei. We
have referred it (pp. 114, 123) to the Flagellates, next to the
Trichonymphidae.

[162] Save the Opalinopsidae, which are usually termed "Opalinidae"; but
which cannot retain the latter name on the removal of the genus
_Opalina_ to the Flagellates.

[163] _Phil. Trans._ clxxxv. 1895, pp. 355 f.

[164] _Arch. Zool. Exp._ (2) vi. vii. 1888-1889.

[165] Calkins has recently found that the vitality within a cycle is
rhythmical, with alternations of more and of less frequent fissions,
under the same set of conditions; and that minute doses of beef-tea
or various mineral salts will not only keep up the higher rate, but
even stave off senescence. Minute doses of alcohol will keep up the
higher rate, but not avert senescence. He considers that Maupas'
generalisations are in most respects too sweeping (_Arch. Entw._ xv.
1902, p. 139). But Dr. James Y. Simpson informs me that the
possibility of stimulative regeneration has been found to be limited.
See also Calkins and Lieb, _Arch. Prot._ i. 1902, p. 355.

[166] As inferred by Hickson from the prolongation of the union.

[167] When there are at the outset two or more micronuclei all undergo the
first two fissions, but only one undergoes the third.

[168] _Zeitschr. wiss. Zool._ xxxiii. 1880, p. 439.

[169] Bezzenberger has given a key to the species of these two genera in
_Arch. Prot._ iii. 1903, pp. 149, 157.

[170] We note that _Lacrymaria_ is prolonged in front into a long, slender
flexible "neck," with the mouth terminal. This swan-like conformation
is "mimicked" by _Dileptus_ and _Lionotus_, where the neck, like the
prostomium of worms, is a mere extension of the front of the body
above and beyond the mouth; all three swim with peculiar grace.
_Trachelius_ (Fig. 56) has a distinct cup-shaped sucker behind the
mouth, and is remarkable, like _Loxodes_, for the branching
disposition of its endosarc.

[171] The pigment of this species has been examined and described by
Lankester under the name of "blue stentorin" (_Quart. Journ. Micr.
Sci._ xii. 1873).

[172] For a full account of _Caenomorpha_, _Metopus_, and allied forms, see
Levander, _Beitr. z. Kenntn. einiger Ciliaten_, Dissert. Helsingfors,
1894.

[173] _Torquatella typica_, described by Lankester as possessing a
continuous undulating membrane for its peristomial wreath, is
identified by Bütschli as a _Strombidium_, possessing exceptionally
large membranellae.

[174] Outside the principal wreath is another of fine cilia ("paroral"),
standing out at an angle.

[175] Covered with a rather lax structureless membrane (sarcolemma), which
is spirally wrinkled when the muscle contracts. I am unable to verify
Geza Entz's observations, adopted by Calkins and Delage.

[176] Of the composition of cellulose (Halliburton, in _Quart. Journ. Micr.
Sci._ xxv. 1885, p. 445).

[177] As does the Hypotrichan _Kerona polyporum_.

[178] Permanently ciliate in _Hypocoma_ and _Suctorella_.

[179] In this case the débris of the live prey torn up by the _Cyclops_ on
which they live.

[180] The spiral ridge figured by Hertwig (Fig. 61, 1. _c_) is probably an
incorrect representation of this structure, exceedingly minute in all
genera but _Choanophrya_.

[181] In _Choanophrya_ I have failed to find any pore, and believe the
bud-formation to be strictly endogenous.

[182] See _Quart. Journ. Micr. Sc._ xlv. 1902, p. 325.

[183] In _Journ. Coll. Sc. Japan_, x. 1896.

[184] _Étude monographique sur le groupe des Tentaculifères, Ann. Soc.
Belge Micr._ xxiv.-xxvi. 1901.

[185] To Professor W. J. Sollas, Sc.D., F.R.S., who undertook to write the
chapters on Porifera when the work was first planned, the Author and
the Editors are indebted for his kind assistance in reading and
criticising this article.

[186] _Rarities belonging to the Royal Society preserved at Gresham
College_, 1686.

[187] _Gerarde's Herbal, enlarged and revised by Thomas Johnson_, 1636, p.
1587.

[188] _Phil. Trans._ lv. p. 280.

[189] _Histoire Phys. de la Mer_, 1725.

[190] _Mem. Boston Soc._ i. 1867, p. 305.

[191] _Zeitschr. wiss. Zool._ xxxi. 1878, p. 262.

[192] _Ann. Mag. Nat. Hist._ (5) xiii. 1884, p. 381.

[193] _Quart. Journ. Micr. Sci._ xxiv. 1884, p. 612.

[194] The name was coined by Dr. Fleming from χάλιξ "silex" and χόνδρος
"cartilage," and as these roots could only give _Chalic-chondria_ it
is not surprising that those who have not referred to Dr. Fleming's
statements give the derivation as ἅλς "sea" and χόνδρος.

[195] _Monograph of British Sponges_, vol. iii. pl. xxxix.-xl. For revision
of nomenclature in this Monograph, see Hanitsch, _Tr. Liverp. Biol.
Soc._ viii. 1894, p. 173.

[196] _Journ. Physiol._ ix. 1888, p. 1.

[197] Sollas, _Ann. Mag. Nat. Hist._ (4) xx. 1877, p. 285; Bütschli,
_Zeitschr. f. wiss. Zool._ xix. 1901, p. 236.

[198] Minchin, "Sponges" in _Treatise on Zoology_, edited by E. Ray
Lankester, p. 87. See also Bidder, _Proc. Roy. Soc._ li. 1892, p.
474.

[199] _Zool. Jahrb. Anat._ vii. 1894.

[200] _Materials for the Study of Variation_, 1894, p. 30.

[201] _Arch. de Zool. Exp._ (2) x. 1892, pp. 345-498. On the general
subject of adhesion of species, see Bowerbank, _Brit. Ass. Rep._
1857, p. 11, who quotes Grant as the first to observe the phenomenon.

[202] _Quart. Journ. Micr. Sci._ xxii. 1882, p. 229.

[203] But see Gamble and Keeble, _Quart. Journ. Micr. Sci._ xlvii. 1904, p.
363, who show that various green animals really owe their colour to
"algae," though the infection with the "alga" is difficult to detect
because it takes place by means of a colourless cell. See also
_Zoochlorella_, on p. 126.

[204] Sollas, _Tr. Dublin Soc._ (2) iii. 1884, p. 87.

[205] _Arch. Naturg._ lix. 1893, p. 246.

[206] Weltner, _Blatt. Aquar. Fr._ vii. 1896, p. 277, and
"Spongillidenstudien," _Arch. Naturg._ ii. 1893, p. 271.

[207] Evans, _Quart. Journ. Micr. Sci._ xliv. 1900, p. 72.

[208] _Ann. Mag. Nat. Hist._ (2), x. 1882, p. 365.

[209] _P. Ac. Philad._ 1887, pp. 158-278.

[210] Evans, _Quart. Journ. Micr. Sci._ xlii. 1899, p. 363.

[211] Francé, _Organismus der Craspedomonaden_, Budapest, 1897, p. 217.

[212] Sollas, _Encyclopædia Britannica_, art. "Sponges," 1887.

[213] Sollas, _Ann. Mag. Nat. Hist._ (5) iii. 1879, p. 23; _Challenger
Report_, vol. xxv. pt. lxiii. 1888, p. lii.

[214] Minchin, Lankester's _Treatise on Zoology_, pt. ii. 1900.

[215] Minchin, _loc. cit._ p. 110.

[216] Bidder, _Quart. Journ. Micr. Sci._ xxxii. 1891, p. 631, and Minchin,
_Quart. Journ. Micr. Sci._ xxxiii. 1892, p. 266.

[217] Minchin, Lankester's _Treatise on Zoology_, p. 30.

[218] Vosmaer and Pekelharing, _Verh. Ak. Amsterdam_, (2) vi. 3, 1898, p.
1.

[219] Dendy, _Quart. Journ. Micr. Sci._ xxxv. 1894, p. 230.

[220] Maas, _Zeitschr. wiss. Zool._ lxvii. 1899-1900, p. 215.

[221] "Die Kalkschwämme," 1871.

[222] Dendy. _loc. cit._ p. 159.

[223] _Quart. Journ. Micr. Sci._ xxxvi. 1894, p. 127.

[224] Doederlein, _Zool. Jahrb. Abth. Anat._ x. 1896, p. 15, pl. ii. and
iii.

[225] Hinde, _Quart. Journ. Geol. Soc._ lvi. 1900, p. 50.

[226] Hinde, _Tr. R. Micr. Soc._ 1904, p. 3.

[227] Počta, _Bull. Acad. Bohème_, 1903.

[228] J. J. Lister in Willey's _Zoological Results_, pt. iv. 1900, p. 459.

[229] _Mém. Soc. Zool. France_, 1896, p. 119.

[230] _Arch. Zool. Exp._ (3) iii. 1895, p. 561, pl. xxiii.

[231] F. E. Schulze, _Challenger Monograph_, xxi.

[232] Chun, "Aus den Tiefen des Weltmeeres," 1900, p. 481.

[233] Shipley, "Fauna of the Antarctic Regions." See also p. 216.

[234] _J. Coll. Japan_, xv. 1901, pp. 128, 147, 190.

[235] _Fauna Arctica_ (Roemer and Schaudinn), i. 1900, p. 84; and _Sitzb.
Akad. Berlin_, 1899, p. 98.

[236] Sollas, _Quart. Journ. Geol. Soc._ 1880, p. 362.

[237] _Quart. Journ. Geol. Soc._ xl. 1884, p. 795.

[238] "Monograph British Fossil Sponges," _Palaeont. Soc._ xl. and xli.
1887 and 1888.

[239] Sollas, _Challenger Monograph_, xxv. 1888.

[240] _Marine Investigations in South Africa_, i. 1902, p. 224.

[241] Cf. Sollas, _Encyclopædia Britannica_, 1887, art. "Sponges," and
Schrammen, _Mitth. Mus. Hildesheim_, 14, 1901.

[242] Sollas, _Quart. Journ. Geol. Soc._ xxxiii. 1877, p. 790.

[243] Ridley and Dendy, _Challenger Monograph_, lix. 1887.

[244] _Ibid._ p. 262; cf. also p. 197.

[245] _Quart. J. Micr. Sci._ xli. 1901, p. 477.

[246] Loisel, _J. de l'Anat. et Phys._ xxxiv. 1898, p. 1.

[247] R. v. Lendenfeld, _Acta Ac. German._ lxix. 1896, p. 22.

[248] _Challenger Report_, lix. 1887, p. 214.

[249] Topsent, _Zoologie Descriptive_, i.; also Cotte, _C. R. Soc. Biol.
Paris_, 1902, pp. 638-639.

[250] Topsent, _Arch. Zool. Exp._ (3) viii. 1900, p. 36.

[251] Sollas, _Challenger Monograph_, xxv. pt. lxiii. 1888, p. lxxxix.

[252] Topsent, _Arch. Zool. Exp._ (3) viii. 1900, p. 226. For an account of
certain very remarkable structures termed diaphragms in _Cliona
mucronata_ and _C. ensifera_, see Sollas, _Ann. Mag. Nat. Hist._ (5)
i. 1878, p. 54.

[253] R. von Lendenfeld, _Monograph of Horny Sponges_, 1889, p. 831.

[254] Cf. Minchin in E. Ray Lankester's _Treatise_, p. 77.

[255] Maas, _Zool. Centralbl._ v. 1898, p. 581.

[256] _Arch. Zool. Exp._ viii. 1879, p. 59.

[257] "Biological Lectures, Wood's Holl," 1894, p. 43.

[258] F. E. Schulze, _Zool. Anz._ ii. 1879, p. 636.

[259] Maas, _Zeitschr. wiss. Zool._ lxx. 1901, p. 263.

[260] Maas, _loc. cit._ p. 284.

[261] _J. Coll. Japan_, xv. 1901, p. 180.

[262] Perkins, _Johns Hopkins Univ. Circ._ xxi. 1902, p. 87.

[263] For details of this interesting process see Minchin, _Quart. J. Micr.
Sci._ xl. 1898, p. 469.

[264] Maas, _Zeitschr. wiss. Zool._ lxvii. 1900, p. 225.

[265] Maas, _SB. Ak. München_, xxx. 1900, p. 553, and _Zeitschr. wiss.
Zool._ lxx. 1901, p. 265; see also Sollas, _Ann. Mag. Nat. Hist._ (5)
ix. 1880, p. 401.

[266] Sollas, _Challenger Monograph_, xxv. 1888, p. xlv.

[267] Sollas, _ibid._ pp. 13 and 34, pl. v.

[268] _Zeitschr. wiss. Zool._ lii. 1891, p. 294.

[269] I. Sollas, _P. Zool. Soc. London_, ii. 1902, p. 215.

[270] Sollas, _Ann. Mag. Nat. Hist._ (5) ix. 1880, p. 402.

[271] Bowerbank, and also Vosmaer and Pekelharing, _Verh. Ak. Amsterdam_
(2) vi. 3, 1898.

[272] _J. Coll. Japan_, xv. 1901, p. 193.

[273] Vosmaer and Pekelharing, _Verh. Ak. Amsterdam_, 1898.

[274] See Bidder, _P. Camb. Soc._ vi. 1888, p. 183; Sollas, _Challenger
Monograph_, xxv. 1883, pp. xviii.-xxi.; and Vosmaer and Pekelharing,
_loc. cit._

[275] Carter and Lieberkühn in 1856, Haeckel in 1872, Metschnikoff in 1879,
and many later workers.

[276] _Die Kalkschwämme_, 1872, i. p. 372.

[277] _J. Anat. Physiol._ 1898, pp. 1, 6, 234.

[278] _Mém. Ac. St. Pétersb._ (7) xxvi. 1878, p. 10.

[279] Sollas, _Challenger Report_, xxv. pt. lxiii. p. lxxxviii.

[280] _Vergl. Physiologie d. niederen Thiere_, 1903, p. 441.

[281] For further details see Zittel, _Lehrbuch der Palaeontologie_, and
Felix Bernard, _Eléments de Palaeontologie_, 1894.

[282] For further details see Sollas, "The Formation of Flints," in _The
Age of the Earth_, 1905, p. 131.

[283] _Willey's Zool. Results_, pt. ii. 1899, p. 127.

[284] Murbach, _Archiv f. Naturg._ lx. Bd. i. 1894, p. 217.

[285] G. H. Grosvenor, _Proc. Roy. Soc._ lxxii. 1903, p. 462.

[286] H. Jung, _Morph. Jahrb._ viii. 1881, p. 339.

[287] _Verh. Ver. Rheinland_, xlix. 1893, pp. 13, 14, 40, 41.

[288] For an account of the development and of the chitinous membrane see
A. Brauer, _Zeitschr. f. wiss. Zool._ lii. 1891, p. 9.

[289] Trembley, _Mémoires pour servir à l'Histoire d'un genre de Polypes
d'eau douce_, 1744.

[290] G. Wagner, _Quart. Journ. Micr. Sci._ xlviii. 1905, p. 589.

[291] See p. 126.

[292] _Hydra pallida_, Beardsley, has been found to be very destructive to
the fry of the Black-spotted Trout in Colorado, _U.S. Fish. Rep.
Bull._ 1902, p. 158.

[293] For figures of _Protohydra_ see Chun, Bronn's _Thier-Reich_,
"Coelenterata," 1894, Bd. ii. pl. ii.

[294] _Sitzber. Ges. naturf. Freunde Berlin_, ix. 1894, p. 226.

[295] M. Ussov, _Morph. Jahrb._ xii. 1887, p. 137.

[296] This organism is usually described as a fungus (_Achlya_), but it is
probably a green Alga. See J. E. Duerden, _Bull. Amer. Mus. Nat.
Hist._ xvi. 1902, p. 323.

[297] _Bibl. Univ. de Genève, Arch. des Sciences_, v. 1859, p. 80.

[298] _Phil. Trans._ cxlvii. 1876, p. 117.

[299] S. J. Hickson, _Willey's Zool. Results_, pt. ii. 1899, p. 127.

[300] _Quart. Journ. Micr. Sci._ xlii. 1899, p. 341.

[301] "Gymnoblastic Hydroids," _Ray Society_, 1871, p. 359.

[302] Hincks, _British Hydroid Zoophytes_, 1868, p. 74.

[303] _Ann. Mag. Nat. Hist._ (6) x. 1892, p. 207.

[304] Fewkes, _Bull. Mus. Comp. Zool._ xiii. 1887, p. 224.

[305] Hartlaub, _Wiss. Meeresunt. deutsch. Meere in Kiel_ N.F.I. 1894, p.
1.

[306] Carter, _Ann. Mag. Nat. Hist._ (4) xix. 1877, p. 44; (5) i. 1878, p.
298.

[307] The aberrant genus _Hypolytus_ (p. 262) may belong to this family.

[308] Spencer, _Trans. Roy. Soc. Vict._ 1892, p. 8.

[309] _Journ. Coll. Sci. Tokyo_, xiii. 1900, p. 235 (with a beautiful
coloured illustration).

[310] _Proc. Zool. Soc._ 1897, p. 818.

[311] _Zeitschr. f. wiss. Zool._ lxiii. 1898, p. 489.