Marcus Manuel Hartog

“ Encystment, or at least a resting stage at full growth, is very characteristic, and frequently an excretion of granules takes place into the first-formed cyst, whereupon a second inner cyst is formed which may be followed by a third. These brood-cysts, in which multiple fission takes place, may be of two kinds, ordinary and resting, the latter being distinguished by a firm, and usually ornamented and cuticularized cell-wall, and only producing its zoo spores after an interval. ”

“ 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. ”

“ Fusion or conjugation of adult Radiolaria, whether preliminary to swarm-spore-production or independently of it, has not been observed—this affording a distinction between them and Heliozoa.
“Simple fission of the central capsule of adult individuals, preceded of course by nuclear fission, and subsequently of the whole protoplasmic mass, has been observed in several genera of Acantharia and Phaeodaria, and is probably a general method of reproduction in the group. In Spumellaria it gives rise to colonial ‘Polycyttarian’ forms when the extra capsular protoplasm does not divide. ”

“ In all cases the protoplasm from the pylome may deposit additional matter on the outside of the shell, so as to produce very characteristic sculpturing of the surface.
Compound or “polythalamic” shells derive their general form largely from the relations of successive chambers in size, shape and direction. This is well shown in the porcellanous Miliolidae. If we call the straight line uniting the two ends of a chamber the “polar axis,” we find that successive chambers have their pylomes at alternate poles; but they lie on different meridians. ”

“ 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. ”

“ The nucleus is single in the Nuda and Allogromidia and in the megalospheric forms of higher Foraminifera; but microspheric forms when adult contain many simple similar nuclei. The nucleus in every case gives off granules and irregular masses (“chromidia”) of similar reactions, which play an important part in reproduction. During the maturation of the microsphere the nuclei disappear ”

“ It is important to note that the skeleton of silex or acanthin does not correspond to the shell of other Sarcodina, which appears rather to be represented by the membranous central capsule. The skeleton does, however, appear to correspond to the spicules of Heliozoa, and there is an undeniable affinity between such a form as Clathrulina and the Sphaerid Peripylaea (such as Heliosphaera, fig. III. 14) . The Radiolaria are, however, a very strongly marked group, definitely separated from all other Sarcodina by the membranous central capsule sunk in their protoplasm. ”

“ Haemosporidia, &c.) a wriggling, sickle-shaped cell, that growth takes place in the whole surface of the body, and not by ingestion of food and consequently without the active deformations that characterize Sarcodina, and that the life-cycle embraces at least two alternating modes of brood formation.
The subdivision of the phylum is no less difficult. The character of the pseudopods (see Amoeba) is the most obvious one to select, as it appears to be fairly constant. ”

“ Order 5.—EUGLENACEAE. Vacuole large, a reservoir for one or more accessory vacuoles, contractile and opening to the surface by a canal (“pharynx”) in which are planted one or two strong flagella; pellicle strong often striated; nucleus large, chromatophores green, complex or absent; reserves paramylum granules of definite shape, and oil; nutrition variable; body stiff or “metabolic,” never amoeboid. Among the true Flagellates these are the largest, few being below 40 μ and several attaining 130 μ in length of cell-body (excluding flagellum) . ”

“ Archerina boltoni is remarkable for containing a pair of chlorophyll corpuscles in each cell; no nucleus has been made out, but the chlorophyll bodies divide previous to fission. It is a fresh-water form. The cells of this species form loose aggregates or filoplasmodia, like those of Mikrogromia (Foraminifera, q.v.) or Leydenia (Labyrinthuloidea, q.v.) , &c.
Vampyrella (figs. 1–3) and Enteromyxa also form a compact plasmodium which separates into 1-nucleate cells, which then encyst and divide into a brood of four. ”

“ These zoospores are amoeboid; they soon secrete a shell and reveal themselves as megalospheres, the original state of the megalospheric forms. In the adult megalosphere the solitary nucleus disappears and is replaced by hosts of minute vesicular nuclei, formed by the concentration of chromidia. Each nucleus aggregates around it a proper zone of dense protoplasm; by two successive mitotic divisions each mass becomes quadri-nucleate, and splits up into four biflagellate, uninucleate zoospores. These are pairing-cells or gametes, though they will not pair with members of the same brood. ”

“ In Asplanchnaceae the germary is median, continuous at the distal end with the middle of the transverse horseshoe-shaped vitellary. In Bdelloidaceae and Seisonaceae the whole organ is paired, the germary proximal, the vitellary next the cloaca. As a rule, the wall of the ovary is continued into a uterine tube opening into the cloaca; but in Philodinaceae this is absent, and the young are free in the body cavity and escape by perforating the cloacal walls. The male organs are usually a testis, a large seminal bladder and a protrusible penis. The males are unlike the females in most species ”

“ An anterior lateral trailing flagellum may modify this axial rotation, and help in steering. When the animal is at rest—attached by its base or with its body so curved as to resist onward motion—the current produced by the tractellum will bring suspended particles up against the protoplasm at its base of insertion. As noted by E. R. Lankester, the posterior flagellum of many Haemoflagellates, like that of the spermatozoon of Metazoa, propels the cell by a sculling motion behind ”

“ Pseudopods usually granular, fine flexible, tapering generally, not freely branching; reproducing sometimes by simple fission, but more frequently by multiple fission in a brood-cyst whose walls may be multiple. Plasmodium formation occasional, but never leading to the formation of a massive fructification: other syngamic processes unknown, and probably non-existent. ”

“ F. Schaudinn compares the nuclei of the adult Foraminifera with the (vegetative) meganucleus of Infusora (q.v.) and the chromidial mass with the micronucleus, whose chief function is reproductive.
Since megalospheric forms are by far the most abundant, it seems probable that under most conditions they also give rise to megalospheric young like themselves; and that the production of zoospores, pairing to pass into the microspheric form, is only occasional, and possibly seasonal. This life-history we owe to the researches of Schaudinn and J.J. Lister. ”

“ 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. ”

“ Appendix.—The Xenophyophoridae are a small group of bottom-dwelling Sarcodina which show a certain resemblance to arenaceous Foraminifera, though observations in the living state show that the character of the pseudopodia is lacking. The multinucleate protoplasm is contained in branching tubes, aggregated into masses of definite form, bounded by a common wall of foreign bodies (sponge spicules, &c.) cemented into a membrane. The cytoplasm contains granules of BaSO4 and pellets of faecal matter. All that is known of reproduction is the resolution of the pellets into uninucleate cells. ”

“ 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. ”

“ Calcituba, a porcellanous type, which after forming the embryonic chamber with its deflected pylome grows into branching stems, may fall apart into sections, or the protoplasm may escape and break up into small amoebulae. Of the reproduction of the simplest forms we know little. In Mikrogromia the cell undergoes fission within the test, and on its completion the daughter-cells may emerge as biflagellate zoospores. ”

“ There is often a distinction, clear, but never sharp, between the richly vacuolate, almost frothy ectoplasm and the denser endoplasm. One or more contractile vacuoles may protrude from the ectoplasm. The endoplasm contains the nucleus or nuclei. The nucleus when single may be central or excentric: in the latter case, the endoplasm contains a clear central sphere (“centrosome”) on which abut the axial filaments of the pseudopods. ”

“ Protoplasmic Body and Reproduction.—The protoplasm is not differentiated into ecto- and endosarc, although it is often denser in the central part within the shell, and clearer in the pseudopodial ramifications and the layer (or stalk in the monothalamic forms) from which it is given off. In pelagic forms like Globigerina the external layer is almost if not quite identical in structure with the extracapsular protoplasm of Radiolaria (q.v.) ”

“ 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. ”

“ The animal usually forms a simple shell only after it has attained a certain size, and this “embryonic chamber” cannot grow further. In Spirillina and Ammodiscus there is no pylomic end-wall, and the shell continues to grow as a spiral tube; in Cornuspira (fig. 3, 1) there is a slight constriction indicating the junction of a small embryonic chamber with a camptopyle, but the rest of the shell is a simple flat spiral of several turns. In the majority at least one chamber follows the first, with its own pylome at the distal end. ”

“ 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. ”

“ Their shell is either thin or extended many times by long slender tapering spines, and the protoplasm outside has the same character as that of the Radiolaria (q.v.) , being differentiated into jelly containing enormous vacuoles and traversed by reticulate strands of granular protoplasm. These coalesce into a peripheral zone from which protrude the pseudopods, here rather radiate than reticulate. Most genera and most species are cosmopolitan; but local differences are often marked. Foraminifera abound in the shore sands and the crevices of coral reefs. ”

“ 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” ”

“ Thus the majority are littoral or deep-sea, sometimes attached to other bodies or even burrowing in the tests of other Foraminifera; most of the fresh-water forms are sapropelic, inhabiting the layer of organic débris at the surface of the bottom mud ditches of pools, ponds and lakes. The deep-sea species below a certain depth cannot possess a calcareous shell, for this would be dissolved ”

“ 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. ”

“ 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. ”

“ Nervous System.—There is a large ganglion lying in close contact with the pharynx, proximal to the crop and on its antero-dorsal side; in Bdelloidaceae at least it is united by short connectives with a smaller postero-ventral ganglion to form a nerve collar. From this simple nerve fibres are given off to the body-wall, especially to the ciliated cells of the corona, to the foot, and also to the muscles and sense organs.
The sense organs are eyes, antennae, sensory styles and a statocyst in a few species. ”

“ 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. ”

“ 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.
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. ”

“ 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. ”

“ It may, however, well be that the capacity for wintering in the dry state has physiologically replaced the need for resistant fertilized eggs. Insemination takes place either by the introduction of the penis into the cloaca of the female, or by the puncture of the bodywall of the female by the penis, and the injection of the sperm into the body cavity, whence the single spermatozoa must make their way to the eggs. The females habitually produce eggs without impregnation, which again habitually develop into females, more rarely into males. ”

“ Equal conjugation was demonstrated fully by F. Schaudinn in Actinophrys; two individuals approach and enter into close contact, and are surrounded by a common cyst wall. The nucleus of either male divides; and one nucleus passes to the surface at either side, and is budded off with a small portion of the cytoplasm as an abortive cell ”

“ Other types of reproduction are known, Amoeba coli, an inhabitant of the gut of man, showing an endogamous pairing of closely related nuclei similar to that of Actinosphaerium (see Heliozoa) .
Classification
Lobosa.—W. B. Carpenter. Cytoplasm with a clear ectosarc, not wetted by the medium; pseudo pods never finely branching, usually rounded at the apex; nucleus single or multiple; shell (“test,” “theca”) absent, gelatinous, membranous or of cemented granules of ingested sand, &c., or plates secreted in the endosarc. ”

“ 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. ”

“ The “pylome,” or aperture for the protrusion of the protoplasm, is usually single. There are two pylomes at opposite poles in several Filosa (Ditrema) , hence united by some authors into a distinct family (fig. 7, 1, 5, 11) , and in the gelatinous theca of Trichosphaerium (fig. 5) are numerous permanent pylomic pores. The nucleus is variable in form and character. ”

“ They are characterized by the radiate pseudopods, finely tapering at the apex, springing abruptly from the superficial protoplasm, containing a denser, rather permanent axial rod (figs. 1 (1) , 2 (2) ) ; protoplasm without a clear ectoplasm or pellicle, often frothy with large vacuoles, like the alveoli of Radiolaria; nucleus 1 or numerous; skeleton absent, gelatinous or of separate siliceous fibres, plates or spicules, rarely complete and latticed; reproduction by simple fission or by brood-formation, often syngamous; form usually nearly spherical, rarely changing slowly. ”

“ 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. ”

“ Another mode is that of A. radiosa (fig. 1, 1-3) , which can roll over on the tips of its stiff pseudopods. The pseudopods of the Filosa (figs. 6, 7) are branched, but less rich in granules, and less viscid than those of Foraminifera; they rarely anastomose, and never coalesce to form perforated plates.
A process whose relations to reproduction are not fully made out is that of “plastogamy,” where two or more individuals unite completely by their cytoplasm, the nuclei remaining distinct ”

“ 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. ”

“ Conjugation is entirely unknown in Proteomyxa, Labyrinthulidea and Myxomycetes, even at stages where it occurs in other groups, and it has only been definitely made out in a very limited number of genera in the remaining groups. The zygote or product of cell fusion is usually here, as in the majority of types of conjugation, a resting cell. ”

“ Following upon the stomach there is a longer or shorter intestine, which ends in the cloaca. The intestine is lined by ciliated cells. In forms living in a tube the intestine turns round and runs forward, the cloaca being placed so as to debouch over the margin of the tube. The cloaca is often very large; the nephridia and oviducts may open into it, and the eggs lodge there on their way outwards; they are thrown out, as are the faecal masses, by an eversion of the cloaca. ”

“ Several species (e.g. Raphidiophrys elegans) remain associated by the union of their pseudopods, whether into social aggregates (due to approximation) or “colonies” due to lack of separation after fission, is not accurately known. The multinuclear species Actinosphaerium eichhornii (fig. 2) , normally apocytial (i.e. the nuclei divide repeatedly without division of the cytoplasm) , may increase in size by the fusion (“plastogamic”) of small individuals. If a large specimen be cut up or fragment itself under irritation, the small ones so produced soon approach one another and fuse completely. ”