Chapter XIII: Act 1890: , the effect of which is explained in the article Insanity. Any (9)

Perhaps the most marked feature of influenza, and certainly the one which victims have learned to dread most, is the prolonged debility and nervous depression that frequently follow an attack. It was remarked by Nothnagel that "Influenza produces a specific nervous toxin which by its action on the cortex produces psychoses." In the Paris epidemic of 1890 the suicides increased 25%, a large proportion of the excess being attributed to nervous prostration caused by the disease. Dr Rawes, medical superintendent of St Luke's hospital, says that of insanities traceable to influenza melancholia is twice as frequent as all other forms of insanity put together. Other common after-effects are neuralgia, dyspepsia, insomnia, weakness or loss of the special senses, particularly taste and smell, abdominal pains, sore throat, rheumatism and muscular weakness. The feature most dangerous to life is the special liability of patients to inflammation of the lungs. This affection must be regarded as a complication rather than an integral part of the illness. The following diagram gives the annual death-rate per million in England and Wales, and is taken from an article by Dr Arthur Newsholme in _The Practitioner_ (January 1907).

The deaths directly attributed to influenza are few in proportion to the number of cases. In the milder forms it offers hardly any danger to life if reasonable care be taken, but in the severer forms it is a fairly fatal disease. In eight London hospitals the case-mortality among in-patients in the 1890 outbreak was 34.5 per 1000; among all patients treated it was 1.6 per 1000. In the army it was rather less.

The infectious character of influenza having been determined, suggestions were made for its administrative control on the familiar lines of notification, isolation and disinfection, but this has not hitherto been found practicable. In March 1895, however, the Local Government Board issued a memorandum recommending the adoption of the following precautions wherever they can be carried out:--

1. The sick should be separated from the healthy. This is especially
important in the case of first attacks in a locality or a household.

2. The sputa of the sick should, especially in the acute stage of the
disease, be received into vessels containing disinfectants. Infected
articles and rooms should be cleansed and disinfected.

3. When influenza threatens, unnecessary assemblages of persons should
be avoided.

4. Buildings and rooms in which many people necessarily congregate
should be efficiently aerated and cleansed during the intervals of
occupation.

There is no routine treatment for influenza except bed. In all cases bed is advisable, because of the danger of lung complications, and in mild ones it is sufficient. Severer ones must be treated according to the symptoms. Quinine has been much used. Modern "anti-pyretic" drugs have also been extensively employed, and when applied with discretion they may be useful, but patients are not advised to prescribe them for themselves.

Sir Wm. Broadbent in a note on the prophylaxis of influenza recommends quinine in a dose of two grains every morning, and remarks: "I have had opportunities of obtaining extraordinary evidence of its protective power. In a large public school it was ordered to be taken every morning. Some of the boys in the school were home boarders, and it was found that while the boarders at the school took the quinine in the presence of a master every morning, there were scarcely any cases of influenza among them, although the home boarders suffered nearly as much as before." He continues, "In a large girls' school near London the same thing was ordered, and the girls and mistresses took their morning dose but the servants were forgotten. The result was that scarcely any girl or mistress suffered while the servants were all down with influenza."

The liability to contract influenza, and the danger of an attack if contracted, are increased by depressing conditions, such as exposure to cold and to fatigue, whether mental or physical. Attention should, therefore, be paid to all measures tending to the maintenance of health. Persons who are attacked by influenza should at once seek rest, warmth and medical treatment, and they should bear in mind that the risk of relapse, with serious complications, constitutes a chief danger of the disease.

In addition to the ordinary text-books, see the series of articles by
experts on different aspects in _The Practitioner_ (London) for
January 1907.

IN FORMÂ PAUPERIS (Latin, "in the character of pauper"), the legal phrase for a method of bringing or defending a case in court on the part of persons without means. By an English statute of 1495 (11 Hen. VII. c. 12), any poor person having cause of action was entitled to have a writ according to the nature of the case, without paying the fees thereon. The statute of 1495 was repealed by the Statute Law Revision and Civil Procedure Act 1883, but its provisions, as well as the chancery practice were incorporated into one code and embodied in the rules of the Supreme Court (O. xvi. rr. 22-31). Now any person may be admitted to sue as a pauper, on proof that he is not worth £25, his wearing apparel and the subject matter of the cause or matter excepted. He must lay his case before counsel for opinion, and counsel's opinion thereon, with an affidavit of the party suing that the case contains a full and true statement of all the material facts to the best of his knowledge and belief, must be produced before the proper officers to whom the application is made. A person who desires to defend as a pauper must enter an appearance to a writ in the ordinary way and afterwards apply for an order to defend as a pauper. Where a person is admitted to sue or defend as a pauper, counsel and solicitor may be assigned to him, and such counsel and solicitor are not at liberty to refuse assistance unless there is some good reason for refusing. If any person admitted to sue or defend as a pauper agrees to pay fees to any person for the conduct of his business he will be dispaupered. Costs ordered to be paid to a pauper are taxed as in other cases. Appeals to the House of Lords _in formâ pauperis_ were regulated by the Appeal (Formâ Pauperis) Act 1893, which gave the House of Lords power to refuse a petition for leave to sue.

INFORMATION (from Lat. _informare_, to give shape or form to, to represent, describe), the communication of knowledge; in English law, a proceeding on behalf of the crown against a subject otherwise than by indictment. A criminal information is a proceeding in the King's bench by the attorney-general without the intervention of a grand jury. The attorney-general, or, in his absence, the solicitor-general, has a right _ex officio_ to file a criminal information in respect of any indictments, but not for treason, felonies or misprision of treason. It is, however, seldom exercised, except in cases which might be described as "enormous misdemeanours," such as those peculiarly tending to disturb or endanger the king's government, e.g. seditions, obstructing the king's officers in the execution of their duties, &c. In the form of the proceedings the attorney-general is said to "come into the court of our lord the king before the king himself at Westminster, and gives the court there to understand and be informed that, &c." Then follows the statement of the offence as in an indictment. The information is filed in the crown office without the leave of the court. An information may also be filed at the instance of a private prosecutor for misdemeanours not affecting the government, but being peculiarly flagrant and pernicious. Thus criminal informations have been granted for bribing or attempting to bribe public functionaries, and for aggravated libels on public or private persons. Leave to file an information is obtained after an application to show cause, founded on a sworn statement of the material facts of the case.

Certain suits might also be filed in Chancery by way of information in the name of the attorney-general, but this species of information was superseded by Order 1, rule 1 of the Rules of the Supreme Court, 1883, under which they are instituted in the ordinary way. Informations in the Court of Exchequer in revenue cases, also filed by the attorney-general, are still resorted to (see _A.-G._ v. _Williamson_, 1889, 60 L.T. 930).

INFORMER, in a general sense, one who communicates information. The term is applied to a person who prosecutes in any of the courts of law those who break any law or penal statute. Such a person is called a common informer when he furnishes evidence on criminal trials or prosecutes for breaches of penal laws solely for the purpose of obtaining the penalty recovered, or a share of it. An action by a common informer is termed a _popular_ or _qui tam_ action, because it is brought by a person _qui tam pro domino rege quam pro se ipso sequitur_. A suit by an informer must be brought within a year of the offence, unless a specific time is prescribed by the statute. The term informer is also used of an accomplice in crime who turns what is called "king's evidence" (see ACCOMPLICE). In Scotland, informer is the term applied to the party who, in criminal proceedings, sets the lord advocate in motion.

INFUSORIA, the name given by Bütschli (following O.F. Ledermüller, 1763) to a group of Protozoa. The name arose from the procedure adopted by the older microscopists to obtain animalcules. Infusions of most varied organic substances were prepared (hay and pepper being perhaps the favourite ones), the method of obtaining them including maceration and decoction, as well as infusion in the strict sense; they were then allowed to decompose in the air, so that various living beings developed therein. As classified by C. G. Ehrenberg in his monumental _Infusionstierchen als volkommene Organismen_, they included (1) Desmids, Diatoms and Schizomycetes, now regarded as essentially Plant Protista or Protophytes; (2) Sarcodina (excluding Foraminifera, as well as Radiolaria, which were only as yet known by their skeletons, and termed Polycystina), and (3) Rotifers, as well as (4) Flagellates and Infusoria in our present sense. F. Dujardin in his _Histoire des zoophytes_ (1841) gave nearly as liberal an interpretation to the name; while C. T. Van Siebold (1845) narrowed it to its present limits save for the admission of several Flagellate families. O. Bütschli limited the group by removing the Flagellata, Dinoflagellata and Cystoflagellata (q.v.) under the name of "Mastigophora" proposed earlier by R. M. Diesing (1865). We now define it thus:--Protozoa bounded by a permanent plasmic pellicle and consequently of definite form, never using pseudopodia for locomotion or ingestion, provided (at least in the young state) with numerous cilia or organs derived from cilia and equipped with a double nuclear apparatus: the larger (mega-) nucleus usually dividing by constriction, and disappearing during conjugation: the smaller (micro-) nucleus (sometimes multiple) dividing by mitosis, and entering into conjugation and giving rise to the cycle of nuclei both large and small of the race succeeding conjugation.

1. _Opalinopsis sepiolae_, Foett.: a parasitic Holotrichous mouthless
Ciliate from the liver of the Squid. a, branched meganucleus; b,
vacuoles (non-contractile).

2. A similar specimen treated with picrocarmine, showing a remarkably
branched and twisted meganucleus (a), in place of several nuclei.

3. _Anoplophrya naidos_, Duj.; a mouthless Holotrichous Ciliate
parasitic in the worm Nais. a, the large axial meganucleus; b,
contractile vacuoles.

4. _Anoplophrya prolifera_, C. and L.; from the intestine of
_Clitellio_. Remarkable for the adhesion of incomplete
fission-products in a metameric series. a, meganucleus.

5. _Amphileptus gigas_, C. and L. (Gymnostomaceae). b, contractile
vacuoles; c, trichocysts (see fig. 2); d, meganucleus; e. pharynx.

6, 7. _Prorodon niveus_, Ehr. (Gymnostomaceae). a, meganucleus; b,
contractile vacuole; c, pharynx with horny cuticular lining.

6. The fasciculate cuticle of the pharynx isolated.

8. _Trachelius ovum_, Ehr. (Gymnostomaceae); showing the reticulate
arrangement of the endosarc, b, contractile vacuoles; c, the
cuticle-lined pharynx.

9, 10, 11, 12. _Icthyophthirius multifilius_, Fouquet
(Gymnostomaceae). Free individual and successive stages of division to
form spores. a, meganucleus; b, contractile vacuoles.

13. _Didinium nasutum_, Müll. (Gymnostomaceae). The pharynx is everted
and has seized a _Paramecium_ as food. a, meganucleus; b, contractile
vacuole; c, everted pharynx.

14. _Euplotes charon_, Müll. (Hypotrichaceae); lateral view of the
animal when using its great cirrhi, x, as ambulatory organs.

15. _Euplotes harpa_, Stein (Hypotrichaceae); h, mouth; x, cirrhi.

16. _Nyctotherus cordiformis_, Stein (a Heterotriceae), parasitic in
the intestine of the Frog; a, meganucleus; b, contractile vacuole; c,
food particle; d, anus; e, heterotrichous band of membranelles; f, g,
mouth; h, pharynx; i, small cilia.]

Thus defined, the Infusoria fall into two groups:--(1) _Ciliata_, with cilia or organs derived from cilia throughout their lives, provided with a single permanent mouth (absent in the parasitic _Opalinopsidae_) flush with the body or at the base of an oral depression, and taking in food by active swallowing or by ciliary action: (2) _Suctoria_, rarely ciliated except in the young state, and taking in their food by suction through protrusible hollow tentacles, usually numerous.

The pellicle of the Infusoria is stronger and more permanent than in
many Protozoa, and sometimes assumes the character of a mail of hard
plates, closely fitting; but even in this case it undergoes solution
soon after death. It is continuous with a firm ectosarc, highly
differentiated in the Ciliata, and in both groups free from coarse
movable granules. The endosarc is semifluid and rich in granules
mostly "reserve" in nature, often showing proteid or fat reactions.
One or more contractile vacuoles are present in some of the marine and
all the freshwater species, and open to the surface by pores of
permanent position: a system of canals in the deeper layers of the
ectoplasm is sometimes connected with the vacucle. The body is often
provided with not-living external formations "stalk" and "theca" (or
"lorica").

The character of the nuclear apparatus excludes two groups both
parasitic and mouthless: (1) the Trichonymphidae, with a single
nucleus of Leidy, parasitic in Insects, especially Termites; (2) the
Opalinidae, with several (often numerous) uniform nuclei, parasitic in
the gut of Batrachia, &c., and producing 1-nuclear zoospores which
conjugate. Both these families we unite into a group of Pseudociliata,
which may be referred to the _Flagellata_ (q.v.). Lankester in the
last edition of this Encyclopaedia called attention to the doubtful
position of _Opalina_, and Delage and Hérouard placed Trichonymphidae
among Flagellates.

The theca or shell is present in some pelagic species (fig. iii. 3, 5)
and in many of the attached species, notably among the Peritricha
(fig. iii. 21, 22, 25, 26) and Suctoria (fig. viii. 11); and is found
in some free-swimming forms (fig. iii. 3, 5): it is usually chitinous,
and forms a cup into which the animal, protruded when at its utmost
elongation, can retract itself. In _Metacineta mystacina_ it has
several distinct slits (pylomes) for the passage of tufts of
tentacles. In _Stentor_ it is gelatinous; and in the Dictyocystids it
is beautifully latticed.

The stalk is usually solid, and expanded at the base into a disk in
Suctoria. In Peritrichaceae (fig. iii. 8-22, 25, 26), the only ciliate
group with a stalk, it grows for some time after its formation, and on
fission two new stalks continue the old one, so as to form a branched
colony (fig. iii. 18). In _Vorticella_ (fig. iii. 11, 12, 14, &c.) the
stalk is hollow and elastic, and attached to it along a spiral is a
prolongation of the ectosarc containing a bundle of myonemes, so that
by the contractions of the bundle the stalk is pulled down into a
corkscrew spiral, and on the relaxation of the muscle the elasticity
of the hollow stalk straightens it out.

On fission the stalk may become branched, as the solid one of
_Epistylis_ and _Opercularia_ (fig. iii. 20); and the myoneme also in
the tubular stem of _Zoothaminum_; or the branch-myoneme for the one
offspring may be inserted laterally on that for the other in
_Carchesium_ (fig. iii. 18). In several tubicolous Peritrichaceae
there is some arrangement for closing their tubes. In _Thuricola_
(fig. iii. 25-26) there is a valve which opens by the pressure of the
animal on its protrusion, and closes automatically by elasticity on
retraction. In _Lagenophrys_ the animal adheres to the cup a little
below the opening, so that its withdrawal closes the cup: at the
adherent part the body mass is hardened, and so differentiated as to
suggest the frame of the mouth of a purse. In _Pyxicola_ (fig. iii.
21-22) the animal bears some way down the body a hardened shield
("operculum") which closes the mouth of the shell on retraction.

1, Surface view of _Paramecium_, showing the disposition of the
cilia in longitudinal rows.

2, a, mega-; b, micronucleus; c, junction of ecto- and endosarc; D,
pellicle; E, endosarc; f, cilia (much too numerous and crowded); g,
trichocysts; g', same with thread; h, discharged; i, pharynx, its
undulating membrane not shown; k, food granules collecting into a
bolus; l, m, n, o, food vacuoles, their contents being digested as
they pass in the endosarc along the path indicated by the arrows.

3, Outline showing contractile vacuoles in commencing diastole,
surrounded by five afferent canals.

4-7 Successive stages of diastole of contractile vacuole.]

The cytoplasm of the Infusoria is very susceptible to injuries; and
when cut or torn, unless the pellicle contracts rapidly to enclose the
wounded surface, the substance of the body swells up, becoming frothy,
with bubbles which rapidly enlarge and finally burst; the cell thus
disintegrates, leaving only a few granules to mark where it was. This
phenomenon, observed by Dujardin, is called "diffluence." The
contractile vacuole appears to be one of the means by which diffluence
is avoided in cells with no strong wall to resist the absorption of
water in excess; for after growing in size for some time, its walls
contract suddenly, and its contents are expelled to the outside by a
pore, which is, like the anus, usually invisible, but permanent in
position. The contractile vacuole may be single or multiple; it may
receive the contents of a canal, or of a system of canals, which only
become visible at the moment of the contraction of the vacuole (fig.
ii. 4-7), giving liquid time to accumulate in them, or when the
vacuole is acting sluggishly or imperfectly, as in the approach of
asphyxia (fig. ii. 3). Besides this function, since the system passes
a large quantity of water from without through the substance of the
cell, it must needs act as a means of respiration and excretion. In
all Peritrichaceae it opens to the vestibule, and in some of them it
discharges through an intervening reservoir, curiously recalling the
arrangements in the Flagellate Euglenaceae.

The nuclear apparatus consists of two parts, the meganucleus, and the
micronucleus or micronuclei (fig. iii. 17d, iv. 1). The meganucleus
alone regarded and described as "the nucleus" by older observers is
always single, subject to a few reservations. It is most frequently
oval, and then is indented by the micronucleus; but it may be lobed,
the lobes lying far apart and connected by a slender bridge or
moniliform, or horseshoe-shaped (Peritrichaceae). It often contains
darker inclusions, like nucleoles.

It has been shown, more especially by Gruber, that many Ciliata are
multinucleate, and do not possess merely a single meganucleus and a
micronucleus. In _Oxytricha_ the nuclei are large and numerous (about
forty), scattered through the protoplasm, whilst in other cases the
nucleus is so finely divided as to appear like a powder diffused
uniformly through the medullary protoplasm (_Trachelocerca_). Carmine
staining, after treatment with absolute alcohol, has led to this
remarkable discovery. The condition described by Foettinger in his
_Opalinopsis_ (fig. i. 1, 2) is an example of this pulverization of
the nucleus. The condition of pulverization had led in some cases to a
total failure to detect any nucleus in the living animal, and it was
only by the use of reagents that the actual state of the case was
revealed. Before fission, whatever be its habitual character, it
condenses, becomes oval, and divides by constriction; and though it
usually is then fibrillated, only in a few cases does it approach the
typical mitotic condition. The micronucleus described by older writers
as the "nucleolus" or "paranucleus" ("endoplastule" of Huxley), may be
single or multiple. When the meganucleus is bilobed there are always
two micronuclei, and at least one is found next to every enlargement
of the moniliform meganucleus. In the fission of the Infusoria, every
micronucleus divides by a true mitotic process, during which, however,
its wall remains intact. From their relative sizes the meganucleus
would appear to discharge during cell-life, exclusively, the functions
of the nucleus in ordinary cells. Since in conjugation, however, the
meganucleus degenerates and is in great part either digested or
excreted as waste matter, while the new nuclear apparatus in both
exconjugates arises, as we shall see, from a conjugation-nucleus of
exclusively micronuclear origin, we infer that the micronucleus has
for its function the carrying on of the nuclear functions of the race
from one fission cycle to the next from which the meganucleus is
excluded.

Fission is the ordinary mode of reproduction in the Infusoria, and is
usually transverse, but oblique in _Stentor_, &., as in Flagellata,
longitudinal in Peritrichaceae; in some cases it is always more or
less unequal owing to the differentiation of the body, and
consequently it must be followed by a regeneration of the missing
organs in either daughter-cell. In some cases it becomes very uneven,
affording every transition to budding, which process assumes especial
importance in the Suctoria. Multiple fission (brood-formation or
sporulation) is exceptional in Infusoria, and when it occurs the
broods rarely exceed four or eight--another difference from
Flagellata. The nuclear processes during conjugation suggest the
phylogenetic loss of a process of multiple fission into active
gametes. As noted, in fission the meganucleus divides by direct
constriction; each micronucleus by a mode of mitosis. The process of
fission is subject in its activity to the influences of nutrition and
temperature, slackening as the food supply becomes inadequate or as
the temperature recedes from the optimum for the process. Moreover, if
the descendants of a single animal be raised, it is found that the
rapidity of fission, other conditions being the same, varies
periodically, undergoing periods of depression, which may be followed
by either (1) spontaneous recovery, (2) recovery under stimulating
food, (3) recovery through conjugation, or (4) the death of the cycle,
which would have ensued if 2 or 3 had been omitted at an earlier
stage, but which ultimately seems inevitable, even the induction of
conjugation failing to restore it. These physiological conditions were
first studied by E. Maupas, librarian to the city of Algiers, in his
pioneering work in the later 'eighties, and have been confirmed and
extended by later observers, among whom we may especially cite G. N.
Calkins.

Syngamy, usually termed conjugation or "karyogamy," is of exceptional
character in the majority of this group--the Peritrichaceae alone
evincing an approximation to the usual typical process of the
permanent fusion of two cells (pairing-cells or gametes), cytoplasm to
cytoplasm, nucleus to nucleus, to form a new cell (coupled cell,
zygote).

This process was elucidated by E. Maupas in 1889, and his results,
eagerly questioned and repeatedly tested, have been confirmed in every
fact and in every generalization of importance.

Previously all that had been definitely made out was that under
certain undetermined conditions a fit of pairing two and two occurred
among the animals of the same species in a culture or in a locality in
the open; that after a union prolonged over hours, and sometimes even
days, the mates separated; that during the union the meganucleus
underwent changes of a degenerative character; and that the
micronucleus underwent repeated divisions, and that from the offspring
of the micronuclei the new nuclear apparatus was evolved for each
mate. Maupas discovered the biological conditions leading to
conjugation: (1) the presence of individuals belonging to distinct
stocks; (2) their belonging to a generation sufficiently removed from
previous conjugation, but not too far removed therefrom; (3) a
deficiency of food. He also showed that during conjugation a
"migratory" nucleus, the offspring of the divisions of the
micronucleus, passes from either mate to the other, while its sister
nucleus remains "stationary"; and that reciprocal fusion of the
migratory nucleus of the one mate with the stationary nucleus of the
other takes place to form a zygote nucleus in either mate; and that
from these zygote nuclei in each by division, at least two nuclei are
formed, the one of which enlarges to form a meganucleus, while the
other remains small as the first micronucleus of the new reorganized
animal, which now separates as an "exconjugate" (fig. iv). Moreover,
if pairing be prevented, or be not induced, the individuals produced
by successive fissions become gradually weaker, their nuclear
apparatus degenerates, and finally they cannot be induced under
suitable conditions to pair normally, so that the cycle becomes
extinct by senile decay. In Peritrichaceae the gametes are of unequal
sizes (fig. iii. 11, 12), the smaller being formed by brood fissions
(4 or 8); syngamy is here permanent, not temporary, the smaller (male)
being absorbed into the body of the larger (female); and there are
only two nuclei that pair. Thus we have a derived binary sexual
process, comparable to that of ordinary bisexual organisms.

1, _Spirostomum ambiguum_, Ehr.; on its left side oral groove and
wreath of membranellae; a, moniliform meganucleus; b, position of
contractile vacuole.

2, Group of _Stentor polymorphus_, O. F. Müller; the twisted end of
the peristome indicating the position of the mouth.

3, _Tintinnus lagenula_, Cl. and L., in free shell.

4, _Strombidium claparedii_, S. Kent.

5, Shell of _Codonella campanella_, Haeck.

6, 7, _Torquatella typica_, Lank. (= _Strombidium_ according to
Bütschli); p, oral tube seen through peristomial wreath of
apparently coalescent membranellae.

8. Basal, and 9, side (inverted) views of _Trichodina pediculus_,
Ehr.; a, meganucleus; c, basal collar and ring of hooks; d, mouth;
contractile vacuole and oral tube seen by transparency in 8.

10, _Spirochona gammipara_, Stein; a, meganucleus; g, bud.

11, 12, _Vorticella microstoma_, Ehr.; d, formation of a brood of 8
microgametes c by multiple fission; b, contr. vacuole.

13, Same sp. in binary fission; a, meganucleus.

14, _V. nebulifera_, Ehr.; bud swimming away by posterior wreath,
peristome contracted; e, peristomial disk; f, oral tube.

15, _V. microstoma_; b, contr. vacuole; c, d, two microgametes
seeking to conjugate.

16, _V. nebulifera_, contracted, with body encysted.

17, Same sp. enlarged; c, myonemes converging posteriorly to muscle
of stalk; d, micronucleus.

18, _Carchesium spectabile_, Ehr.; (×50).

19, Nematocysts of _Epistylis flavicans_. Ehr. (after Greeff).

20, _Opercularia stenostoma_, St.; (×200); a small colony showing
upstanding ("opercular") peristomial disk, protruded oral undulating
membranejand cilia in oral tube.

21, 22, _Pyxicola affinis_, S.K., with stalk and theca; x, chitinous
disk, or true "operculum" closing theca in retracted state.

23, 24, _Caenomorpha medusula_, Perty, (×250), with spiral
peristomial wreath.

25, 26, _Thuricola valvata_, Str. Wright, in sessile theca, with
internal valve (v) to close tube, as in gastropod _Clausilia_; owing
to recent fission two animals occupy one tube.]

FIG. iv.--Diagrammatic Sketch of Changes during Conjugation in
Ciliata. (From Hickson after Delage and Maupas.)

1, Two individuals at commencement of conjugation showing
meganucleus (dotted) and micronucleus; successive stages of the
disintegration of the meganucleus shown in all figures up to 9.

2, 3, First mitotic division of micronuclei.

4, 5, Second ditto.

6, One of the four nuclei resulting from the second division again
dividing to form the pairing-nuclei in either mate, while the other
3 nuclei degenerate.

7, Migration of the migratory nuclei.

8, 9, Fusion of the incoming migratory with the stationary nucleus
in either mate.

10, Fission of Zygote nucleus into two, the new mega- and
micronucleus whose differentiation is shown in 11, 12. The vertical
dotted line indicates the separation of the mates.]

CILIATA.--The _Ciliate_ Infusoria represent the highest type of Protozoa. They are distinctly animal in function, and the Gymnostomaceae are active predaceous beings preying on other Infusoria or Flagellates. Some possess shells (fig. iii. 3, 5, 21, 22, 25, 26), most have a distinct swallowing apparatus, and in _Dysteria_ there is a complex jaw--or tooth-apparatus, which needs new investigation. In the active Ciliata we find locomotive organs of most varied kinds: tail-springs, cirrhi for crawling and darting, cilia and membranellae for continuous swimming in the open or gliding over surfaces or waltzing on the substratum (_Trichodina_, fig. iii. 8) or for eddying in wild turns through the water (_Strombidium_, _Tintinnus_, _Halteria_). Their forms offer a most interesting variety, and the flexibility of many adds to their easy grace of movement, especially where the front of the body is produced and elongated like the neck of a swan (_Amphileptus_, fig. iii. 5; _Lacrymaria_).

The cytoplasm is very highly differentiated: especially the ectoplasm
or ectosarc. This has always a distinct elastic "pellicle" or limiting
layer, in a few cases hard, or even with local hardenings that affect
the disposition of a coat of mail (_Coleps_) or a pair of valves
(_Dysteria_); but is usually only marked into a rhomboidal network by
intersecting depressions, with the cilia occupying the centres of the
areas or meshes defined. The cytoplasm within is distinctly
alveolated, and frequently contains tubular alveoli running along the
length of the animal. Between these are dense fibrous thickenings,
which from their double refraction, from their arrangement, and from
their shortening in contracted animals are regarded as of muscular
function and termed "myonemes." Other threads running alongside of
these, and not shortening but becoming wavy in the general contraction
have been described in a few species as "neuronemes" and as possessing
a _nervous_, conducting character. On this level, too, lie the
dot-like granules at the bases of the cilia, which form definite
groups in the case of such organs as are composed of fused cilia; in
the deeper part of the ectoplasm the vacuoles or alveoli are more
numerous, and reserve granules are also found; here too exist the
canals, sometimes developed into a complex network, which open into
the contractile vacuole.

FIG. v.--Diagram 1 illustrating changes during conjugation of
_Colpidium colpoda_. (From Hickson, after Maupas.)

M, Old meganucleus undergoing disintegration.

m, Micronucleus.

N, migratory, and

S, Stationary pairing-nucleus.

M´, M´, the new meganuclei, and

m´, The new micronuclei in the products of the first fission of each
of the exconjugates; the continuous vertical line indicates period
of fusion, its cessation, separation; dotted lines indicate fission;
the spaces lettered 1-7 successive stages in the process; the clear
circles indicate functionless nuclei which degenerate.]

The cilia themselves have a stiffer basal part, probably strengthened
by an axial rod, and a distal flexible lash; when cilia are united by
the outer plasmatic layer, they form (1) "Cirrhi," stiff and either
hook-like and pointed at the end, or brush-like, with a frayed apex;
(2) membranelles, flattened organs composed of a number of cilia fused
side by side, sometimes on a single row, sometimes on two rows
approximated at either end so as to form a narrow oval, the
membranelle thus being hollow; (3) the oral "undulating membrane,"
merely a very elongated membranelle whose base may extend over a
length nearly equal to the length of the animal; such membranes are
present in the mouth oral depression and pharynx of all but
Gymnostomaceae, and aid in ingestion; a second or third may be
present, and behave like active lips; (4) in Peritrichaceae the cilia
of the peristomial wreath are united below into a continuous
undulating membrane, forming a spiral of more than one turn, and fray
out distally into a fringe; (5) the dorsal cilia of Hypotrichaceae are
slender and motionless, probably sensory.

Embedded in the ectosarc of many Ciliates are trichocysts, little
elongated sacs at right angles to the surface, with a fine hair-like
process projecting. On irritation these elongate into strong prominent
threads, often with a more or less barb-like head, and may be ejected
altogether from the body. Those over the surface of the body appear to
be protective; but in the Gymnostomaceae specially strong ones
surround the mouth. They can be injected into the prey pursued, and
appear to have a distinctly poisonous effect on it. They are combined
also into defensive batteries in the Gymnostome _Loxophyllum_. They
are absent from most Heterotrichaceae and Hypotrichaceae, and from
Peritrichaceae, except for a zone round the collar of the peristome.

The openings of the body are the _mouth_, absent in a few parasital
species (_Opalinopsis_, fig. i. 1, 2), the _anus_ and the _pore_ of
the contractile vacuole. The _mouth_ is easily recognizable; in the
most primitive forms of the Gymnostomaceae and some other groups, it
is terminal, but it passes further and further back in more modified
species, thereby defining a ventral, and correspondingly a dorsal
surface; it usually lies on the left side. The anus is usually only
visible during excretion, though its position is permanent; in a few
genera it is always visible (e.g. _Nyctotherus_, fig. i. 16). The pore
of the contractile vacuole might be described in the same terms.

The endoplasm has also an alveolar structure, and contains besides
large food-vacuoles or digestive vacuoles, and shows movements of
rotation within the ectoplasm, from which, however, it is not usually
distinctly bounded. In _Ophryoscolex_ and _Didinium_ (fig. i. 13) a
permanent cavity traverses it from mouth to anus.

FIG. vi.--Diagrammatic view of behaviour of the motile reaction of
Paramecium after meeting a mechanical obstruction at A. (From G. N.
Calkins after H. S. Jennings.) For clearness and simplicity the normal
motion is supposed to be straight instead of spiral.]

Ingestion of food is of the same character in all the Hymenostomata.
The ciliary current drives a powerful stream into the mouth, which
impinges against the endosarc, carrying with it the food particles;
these adhere and accumulate to form a pellet, which ultimately is
pushed by an apparently sudden action into the substance of the
endosarc which closes behind it (fig. ii. 2). In some of the
Aspirotrichaceae accessory undulating membranes play the part of lips,
and there is a closer approximation to true deglutition. The mouth is
rarely terminal, more frequently at the bottom of a depression, the
"vestibule," which may be prolonged into a slender canal, sometimes
called the "pharynx" or "oral tube," ciliated as well as provided with
a membrane, and extending deep down into the body in many
Peritrichaceae.

In Spirostomaceae the "adoral wreath" of membranelles encloses more or
less completely an anterior part of the body, the "peristome," within
which lies the vestibule. This area may be depressed, truncate, convex
or produced into a short obconical disk or into one or more lobes, or
finally form a funnel, or a twisted spiral like a paper cone. In most
Peritrichaceae a collar-like rim surrounds the peristome, and marks
out a gutter from which the vestibule opens; the peristome can be
retracted, and the collar close over it. This rim forms a deep
permanent spiral funnel in _Spirochona_ (fig. iii. 10).

_Movements of Ciliata._--H. S. Jennings has made a very detailed study
of these movements, which resemble those of most minute free-swimming
organisms. The following account applies practically to all active
"Infusoria" in the widest sense.

The position of the free-swimming Infusoria, like that of Rotifers and
other small swimming animals, is with the front end of the body
inclined outward to the axis of advance, constantly changing its
azimuth while preserving its angle constant or nearly so; if advance
were ignored the body would thus rotate so as to trace out a cone,
with the hinder end at the apex, and the front describing the base. On
any irritation, (1) the motion is arrested, (2) the animal reverses
its cilia and swims backwards, (3) it swerves outwards away from the
axis so as to make a larger angle with it, and (4) then swims forwards
along a new axis of progression, to which it is inclined at the same
angle as to the previous axis (figs. vi., vii.). In this way it alters
its axis of progression when it finds itself under conditions of
stimulation. Thus a _Paramecium_ coming into a region relatively too
cold, too hot, or too poor in CO2 or in nutriment, alters its
direction of swimming; in this way individuals come to assemble in
crowds where food is abundant, or even where there is a slight excess
of CO2. This reaction may lead to fatal results; if a solution of
corrosive sublimate (Mercuric chloride) diffuses towards the hinder
end of the animal faster than it progresses, the stimulus affecting
the hinder end first, the axis of progression is altered so as to
bring the animal after a few changes into a region where the solution
is strong enough to kill it. This "motile reaction," first noted by H.
S. Jennings, is the explanation of the general reactions of minute
swimming animals to most stimuli of whatever character, including
light; the practical working out is, as he terms it, a method of
"trial and error." The action, however, of a current of electricity is
distinctly and immediately directive; but such a stimulus is not to be
found in nature. The motile reaction in the Hypotrichaceae which crawl
or dart in a straight line is somewhat different, the swerve being a
simple turn to the right hand--i.e. away from the mouth.

Parasitism in the Infusoria is by no means so important as among
Flagellates. _Ichthyophthirius_ alone causes epidemics among Fishes,
and _Balantidium coli_ has been observed in intestinal disease in Man.
The Isotricheae, among Aspirotrichaceae and the Ophryoscolecidae among
Heterotrichaceae are found in abundance in the stomachs of Ruminants,
and are believed to play a part in the digestion of cellulose, and
thus to be rather commensals than parasites. A large number of
attached species are epizoic commensals, some very indifferent in
choice of their host, others particular not only in the species they
infest, but also in the special organs to which they adhere. This is
notably the case with the shelled Peritrichaceae. _Lichnophora_ and
_Trichodina_ (fig. iii. 8, 9) among Peritrichaceae are capable of
locomotion by their permanent posterior wreath or of attaching
themselves by the sucker which surrounds it; _Kerona polyporum_ glides
habitually over the body of Hydra, as does _Trichodina pediculus_.

Several Suctoria are endoparasitic in Ciliata, and their occurrence
led to the view that they represented stages in the life-history of
these. Again, we find in the endosarc of certain Ciliates green
nucleated cells, which have a cellulose envelope and multiply by
fission inside or outside the animal. They are symbiotic Algae, or
possibly the resting state of a Chlamydomonadine Flagellate
(_Carteria_?), and have received the name _Zoochlorella_. They are of
constant occurrence in _Paramecium bursaria_, frequent in _Stentor
polymorphus_ and _S. igneus_, and _Ophrydium versatile_, and a few
other species, which become infected by swallowing them.

_Classification._

Order I.--Section A.--Gymnostomaceae. Mouth habitually closed;
swallowing an active process; cilia (or membranelles) uniform, usually
distributed evenly over the body; form variable, sometimes of circular
transverse section.

Section B.--Trichostomata. Mouth permanently open against the
endosarc, provided with 1 or 2 undulating membranes often prolonged
into an inturned pharynx; ingestion by action of oral ciliary
apparatus.

Order 2.--Subsection (a).--Aspirotrichaceae. Cilia nearly uniform, not
associated with cirrhi or membranelles, nor forming a peristomial
wreath. Form usually flattened, mouth unilateral. (N.B.--Orders 1, 2
are sometimes united into the single order Holotrichaceae.)

Subsection (b).--Spirotricha. Wreath of distinct membranelles--or of
cilia fused at the base--enclosing a peristomial area and leading into
the mouth.

§§ i.--Wreath of separate membranelles.

Order 3.--Heterotrichaceae; body covered with fine uniform cilia,
usually circular in transverse section.

Order 4.--Oligotrichaceae; body covering partial or wholly absent;
transverse section usually circular.

Order 5.--Hypotrichaceae; body flattened; body cilia represented
chiefly by stiff cirrhi in ventral rows, and fine motionless dorsal
sensory hairs.

Order 6.--§§ ii.--Peritrichaceae. Peristomial ciliary wreath, spiral,
of cilia united at the base; posterior wreath circular of long
membranelles; body circular in section, cylindrical, taper, or
bell-shaped.

_Illustrative Genera (selected)._

1. Gymnostomaceae. (a) Ciliation general or not confined to one
surface. _Coleps_ Ehr., with pellicle locally hardened into mailed
plates; _Trachelocerca_ Ehr.; _Prorodon_ Ehr. (fig. i. 6, 7);
_Trachelius_ Ehr., with branching endosarc (fig. i. 8); _Lacrymaria_
Ehr. (fig. i. 5), body produced into a long neck with terminal mouth
surrounded by offensive trichocysts; _Dileptus_ Duj., of similar form,
but anterior process, blind, preoral; _Ichthyophthirius_ Fouquet (fig.
i. 9-12), cilia represented by two girdles of membranellae; _Didinium_
St. (fig. i. 13), cilia in tufts, surface with numerous tentacles each
with a strong terminal trichocyst; _Actinobolus_ Stein, body with one
adoral tentacle; Ileonema Stokes. (b) Cilia confined to dorsal
surface. _Chilodon_ Ehr.; _Loxodes_ Ehr., body flattened, ciliated on
one side only, endosarc as in _Trachelius_; _Dysteria_ Huxley, with
the dorsal surface hardened and hinged along the median line into a
bivalve shell, ciliated only on ventral surface, with a protrusible
foot-like process, and a complex pharyngeal armature. (c) Cilia
restricted to a single equatorial girdle, strong (probably
membranelles); _Mesodinium_, mouth 4-lobed.

2. Aspirotrichaceae. _Paramecium_ Hill (fig. ii. 1-3); _Ophryoglena_
Ehr.; _Colpoda_ O. F. Müller; _Colpidium_ St.; _Lembus_ Cohn, with
posterior strong cilium for springing; _Leucophrys_ St.; _Urocentrum_
Nitsch, bare, with polar and equatorial zones and a posterior tuft of
long cilia; _Opalinopsis_ Foetlinger (fig. i. 1, 2); _Anoplophyra_
St. (fig. i. 3, 4). (The last two parasitic mouthless genera are
placed here doubtfully.)

3. Heterotrichaceae. (a) Wreath spiral; _Stentor_ Oken. (fig. iii. 2),
oval when free, trumpet-shaped when attached by pseudopods at apex,
and then often secreting a gelatinous tube; _Blepharisma_ Perty,
sometimes parasitic in Heliozoa; _Spirostomum_ Ehr., cylindrical, up
to 1´´ in length; (b) Wreath straight, often oblique; _Nyctotherus_
Leidy, parasitic anus always visible; _Balantidium_ Cl. and L.,
parasitic (_B. coli_ in man); _Bursaria_, O.F.M., hollowed into an
oval pouch, with the wreath inside.

4. Oligotrichaeceae. _Tintinnus_ Schranck (fig. iii. 3);
_Trichodinopsis_ Cl. and L.; _Codonella_ Haeck. (fig. iii. 5);
_Strombidium_ Cl. and L. (fig. iii. 4), including _Torquatella_ Lank.
(fig. iii. 6, 7), according to Bütschli; _Halteria_ Duj., with an
equatorial girdle of stiff bristle-like cilia; _Caenomorpha_ Perty
(fig. iii. 23, 24); _Ophryoscolex_ St., with straight digestive
cavity, and visible anus, parasitic in Ruminants.

5. Hypotrichaceae. _Stylonychia_ Ehr.; _Oxytricha_ Ehr.; _Euplotes_
Ehr. (fig. i. 14, 15); _Kerona_ Ehr. (epizoic on _Hydra_).

6. Peritrichaceae. 1. Peristomial wreath projecting when expanded
above a circular contractile collar-like rim.

(a) Fam. Urceolaridae: posterior wreath permanently present around
sucker-like base. _Trichodina_ Ehr. (fig. iii. 8, 9), epizoic on
Hydra; _Lichnophora_ Cl. and L.; _Cyclochaeta_ Hatchett Jackson;
_Gerda_ Cl. and L.; _Scyphidia_ Duj.

(b) Fam. Vorticellidae = Bell Animalcules: posterior wreath
temporarily present, shed after fixation.

Subfam. 1. Vorticellinae animals naked. (i.) Solitary; _Vorticella_
Linn. (fig. iii. 11-17), stalk hollow with spiral muscle; _Pyxidium_
S. Kent, stalk non-contractile. (ii.) Forming colonies by budding on a
branched stalk: _Carchesium_ Ehr., hollow branches and muscles
discontinuous; _Zoothamnium_. Ehr., branched hollow stem and muscle
continuous through colony; _Epistylis_ Ehr., stalk rigid--(the animal
body in these three genera has the same characters as
_Vorticella_)--_Campanella_ Goldf., stalked like _Epistylis_, wreath
of many turns (nematocysts sometimes present) (fig. iii. 19);
_Opercularia_, stalk of _Epistylis_, disk supporting wreath obconical,
collar very high (fig. iii. 20).

Subfam. 2. Vaginicolinae; body enclosed in a firm theca: _Vaginicola_
Lam., shell simple, sessile; _Thuricola_ St. Wright, shell sessile,
with a valve opening inwards (fig. iii. 25-26); _Cothurnia_ Ehr.,
shell stalked, simple; _Pyxicola_ S. Kent, shell stalked, closed by an
infraperistomial opercular thickening on the body (fig. iii. 21-22).

Subfam. 3. Shells gelatinous; those of the colony aggregated into a
floating spheroidal mass several inches in diameter _Ophrydium_ Bory,
_O. versatile_ contains _Zoochlorella_, which secretes oxygen, and the
gas-bubbles float the colonies like green lumps of jelly.

2. Peristomial wreath, not protrusible, surrounded by a very high
usually spiral collar.

Fam. Spirochonina. _Spirochona_ St. (fig. iii. 10); _Kentrochona_
Rompel; both genera epizoic on gills, &c., of small Crustacea.

SUCTORIA.--These are distinguished from Ciliata by their possession of hollow tentacles (one only in _Rhyncheta_, fig. viii. 1, and _Urnula_) through which they ingest food, and by not possessing cilia, except in the young stage. Fission approximately equal is very rare. Usually it is unequal, or if nearly equal one of the halves remains attached, and the other, as an embryo or gemmule, develops cilia and swims off to attach itself elsewhere; _Sphaerophrya_ (fig. viii. 2-6) alone, often occurring as an endoparasite in Ciliata, may be free, tentaculate and unattached.

The ectosarc is usually provided with a firm pellicle which shows a
peculiar radiate "milling" in optical section, so fine that its true
nature is difficult to make out; it may be due to radial rods,
regularly imbedded, or may be the expression of radial vacuoles. The
tentacles vary in many respects, but are always retractile. They are
tubes covered by an extension of the pellicle; this is invaginated
into the body round the base of the tentacle as a sheath, and then
evaginated to form the outer layer of the tentacle itself, over which
it is frequently raised into a spiral ridge, which may be traced down
into the part sunk and ensheathed within the body: in _Choanophrya_,
where the tentacles are largest, the pellicle is further continued
into the interior of the tentacle. The tentacles are always pierced by
a central canal opening at the apex, which may be (1) enlarged into a
terminal capitate sucker, (2) slightly flared, (3) truncate and closed
in the resting state to become widely opened into a funnel, or (4)
pointed. The tentacles are always capable of being waved from side to
side, or turned in a definite direction for the reception or
prehension of food; in _Rhyncheta_, the movements of the long single
tentacle recall those of an elephant's trunk, only they are more
extensive and more varied. In the majority of cases the food consists
of Ciliata; and the contents of the prey may be seen passing down the
canal of the sucker beyond where it becomes free from the general
surface. In _Choanophrya_ the food appears to consist of the débris of
the prey of the carnivorous host (_Cyclops_), which is sucked into the
wide funnel-shaped mouths of the tentacles--by what mechanism is
unknown. The endosarc is full of food-granules and reserve-granules
(oil, colouring matter and proteid).

1, _Rhyncheta cyclopum_, Zenker; only a single tentacle and that
suctorial; epizoic on Cyclops.

2, _Sphaerophrya urostylae_, Maupas; normal adult; parasitic in
Ciliate _Urostyla_.

3, The same dividing by transverse fission, the anterior moiety with
temporarily developed cilia.

4, 5, 6, _Sphaerophrya stentorea_, Maupas. Parasitic in _Stentor_,
and at one time mistaken for its young.

7, _Trichophrya epistylidis_, Cl. and L.

8, _Hemiophrya gemmipara_, Hertwig. Example with six buds, into each
of which a branch of the meganucleus a is extended.

9, The same species, showing the two kinds of tentacles (the
suctorial and the pointed), and two contractile vacuoles b.

10, Ciliated embryo of _Podophrya steinii_, Cl. and L.

11, _Acineta grandis_, Saville Kent; showing pedunculated cup, and
animal with two bunches of entirely suctorial tentacles.

12, _Sphaerophrya magna_, Maupas. It has seized with its tentacles,
and is in the act of sucking out the juices of six examples of the
Ciliate _Colpoda parvifrons_.

13, _Podophrya elongata_, Cl. and L.

14, _Hemiophrya benedenii_, Fraip.; the suctorial tentacles
retracted.

15, _Dendrocometes paradoxus_, Stein. Parasitic on Gammarus pulex;
captured prey.

16, A single tentacle of _Podophrya_. R. Hertwig.

17-20, _Dendrosoma radians_, Ehr.:--17, free-swimming ciliated
embryo. 18, Earliest fixed condition of the embryo. 19, Later stage,
a single tentaculiferous process now developed. 20, Adult colony; c,
enclosed ciliated embryos; d, branching stolon; e, more minute
reproductive (?) bodies.

21, _Ophryodendron pedicellatum_, Hincks.]

The meganucleus and the micronucleus are both usually single, but in
_Dendrosoma_ (fig. viii. 20), of which the body is branched, and the
meganucleus with it, there are numerous micronuclei. In most cases the
micronucleus has not been recorded, though from the similarity of
conjugation, and its presence in most cases of fission and budding
that have been accurately described, we may infer that it is always
present. In unequal fission the meganucleus sends a process into the
bud, while the micronucleus divides as in Ciliata. The bud may be
nearly equal to the remains of the original animal, or much smaller,
and in that case a depression surrounds it which may deepen so as to
form a brood-cavity, either communicating by a mere "birth-pore" with
the outside or entirely closed. In some cases the budding is multiple
(fig. viii. 8), and a large number of buds are formed and liberated at
the same time. In all cases the bud escapes without tentacles, and
possesses a characteristic supply of cilia, whose arrangement is
constant for the species.

In some cases an adult may withdraw its tentacles, moult its pellicle
and develop an equipment of cilia and swim away: this is the case with
_Dendrocometes_, parasitic on _Gammarus_, when its host moults.

The numerous species of Suctoria, often so abundant on various species
of _Cyclops_, are not found on the other freshwater Copepoda,
_Diaptomus_ and _Canthocamptus_, belonging indeed to other families.
Again, these Suctoria affect different positions, those found on the
antennae not being present on the mouth parts; the ventral part of the
thorax has another set; and the inside of the pleural fold another.
_Rhyncheta_ occupies the front of the "couplers" or median downgrowths
uniting the coxopodites of the swimming legs, and _Choanophrya_
settles in the immediate neighbourhood of the mouth, preferably on the
epistoma, labrum and metastomatic region, but also on the adoral
appendages and in rare cases extends, when the settlement is
extensive, to the bases of the two pairs of antennae; while distinct
species of _Podophrya_ settle on the antennae, the front of the thorax
and the inside of the pleural folds. _Dendrocometes_ is common on the
gills of the freshwater shrimp (Amphipod) _Gammarus_ and
_Stylocometes_ on the gills and gill-covers of the Isopod Asellus, the
water-slater. The independence of the Acinetaria was threatened by the
erroneous view of Stein that they were phases in the life-history of
Vorticellidae. Small parasitic forms (_Sphaerophrya_) were also
regarded erroneously as the "acinetiform young" of Ciliata. They now
must be regarded as an extreme modification of the Protozoon series,
in which the differentiation of organs in a unicellular animal reaches
its highest point.

_Principal Genera._

1. Unstalked simple forms. _Urnula_ Cl. and L., permanently ciliate;
_Rhyncheta_ Zenker (fig. viii. 1), on the limb couplers of _Cyclops_;
_Sphaerophrya_ Cl. and L. (fig. viii. 2-6, 12), endoparasitic in
Ciliata and formerly taken for embryos thereof, never attached;
_Trichophrya_ Cl. and L. (fig. viii. 7), of similar habits, but
temporarily attached, sessile.

2. Stalked simple forms; _Podophrya_ Ehr. (fig. viii. 10, 13, 16),
tentacles all knobbed or flared; _Ephelota_ Strethill Wright,
tentacles all pointed; _Hemiophrya_ S. Kent (fig. viii. 8, 9, 14),
tentacles of both kinds; _Choanophrya_ Hartog, tentacles thick,
truncate, very retractile, when expanded opening into funnels for
aspiration of floating prey, never for attachment--epizoic on
antero-ventral parts of _Cyclops_.

3. Cupped forms; _Solenophrya_ Cl. and L., cup sessile; _Acineta_
Ehr., cup stalked; _Acinetopsis_ Bütschli, like _Acineta_, but the cup
flattened, closed distally with only slit-like apertures ("pylomes")
for the bundles of tentacles; _Podocyathus_, like _Acineta_, but with
pointed as well as knobbed tentacles.

4. Tentacles in bundles at the tips of one or more processes or
branches of the body. _Ophryodendron_ Cl. and L., tentaculiferous
process single (fig. viii. 21); _Dendrocometes_ Stein (fig. viii. 15),
body rounded, processes repeatedly branched, epizoic on gills of
_Gammarus pulex_; _Dendrosoma_ Ehr. (fig. viii. 17-20), body freely
branched from a basal attached stolon, meganucleus branching with the
body.

BIBLIOGRAPHY.--(a) Infusoria in the widest sense: C. E. Ehrenberg.
_Die Infusionstierchen als vollkommene Organismen_ (1838); F.
Dujardin, _Zoophytes infusoires_ (1841). (b) Infusoria, including
Mastigophora: M. Perty, _Zur Kenntniss Kleinster Lebensformen_ (1852);
E. Claparède and J. Lachmann, _Études sur les infusoires_ _et les
Rhizopodes_ (1858-1861); F. von Stein, _Der Organismus der
Infusionstiere_ (1859-1883); W. Saville Kent, _A Manual of the
Infusoria_, including a description of all known Flagellate, Ciliate
and Tentaculiferous Protozoa (1880-1882). (c) Infusoria, as limited by
Bütschli. O. Bütschli, _Bronn's Tierreich_, vol. i. _Protozoa_, pt. 3
_Infusoria_ (1887-1889), the most complete work existing, but without
specific diagnoses; S. J. Hickson, "The Infusoria" in Lankester's
_Treatise on Zoology_, vol. i. fasc. 2 (1903), a general account, well
illustrated, with a diagnosis of all genera. See also Delage and
Hérouard, _Traité de Zoologie concrète_, vol. i. "La Cellule et les
Protozoaires" (1896), with an illustrated conspectus of the genera; E.
Maupas, "Recherches expérimentales sur la multiplication des
Infusoires ciliés," _Arch. zool. exp._ vi. (1888); and "Le
Rajeunissement karyogomique chez les Ciliés," _ib._ vii. (1889); R.
Sand, _Étude monographique sur le groupe des Infusoires
tentaculifères_ (Suctoria), (1899), with diagnoses of species; A.
Lang, _Lehrb. der vergleich, Anatomie der wirbellosen Tiere_, vol. i.
"Protozoa" (1901) (a view of comparative anatomy, physiology and
bionomics); Marcus Hartog, "Protozoa," in _Cambridge Natural History_,
i. (1906); H. S. Jennings, _Contributions to the Study of the
Behaviour of Lower Organisms_ (1904); G. N. Calkins, "Studies on the
Life History of Protozoa" (Life cycle of Paramecium), I. _Arch. Entw._
xv. (1902), II. _Arch. Prot._ i. (1902), III. _Biol. Bull._ iii.
(1902), IV. _J. Exp. Zool._ i. (1904). Numerous papers dealing
especially with advances in structural knowledge have appeared in the
_Archiv für Protistenkunde_, founded by F. Schaudinn in 1902.
(M. Ha.)