FLAGELLATA.] PROTOZOA 857 tractile vacuole ; c, amylon-nucleus ; d, free colourless flagellates, probably not belonging to Dinobryon ; e, stigma (eye-spot); /, chromatophors. 16. Peranema trichophorum, Ehr., (one of the Euglenoidea), creeping individual seen from the back ; x 140. a, nucleus ; b, contractile vacuoles ; c, pharynx ; d, mouth. 17. Anterior end of Euylena acus, Ehr., in profile, a, mouth ; b, contractile vacuoles ; c, pharynx ; rf, stigma (eye-spot); e, paramylum-body ; /, chlorophyll corpuscles. 18. Part of the surface of a colony of Volvox //lobatur, L. (Phytomastigoda), showing the intercellular connective fibrils, a, nucleus ; b, contractile vacuole ; c, amylum granule. 19. Two microgonidia of Volvox ylobator, L. a, nucleus ; b, contractile vacuole. 20. Ripe asexually produced daughter-individual of Voloox minor, Stein, still enclosed in the cyst of the partheno-gonidium. a, young partheno-gonidla. 21, 22. Tn/panosoma scmguinig, Gruby ; one of the Rhizomastigina, from the blood of Rana esculenta. a, nucleus. x 500. 23-26. Repro duction of Budo caudatus, Duj. (one of the Heteromastigoda), after Dallin- ger and Drysdale : 23, fusion of several individuals (plasmodium) ; 24, encysted fusion-product dividing into four ; 25, later into eight ; 26, cyst filled with swarm-spores. 27. Astasia tcnax, O. F. Mull. (Proteus) ; one of the Euglenoidea ; x 440. Individual with the two tiagella, and strongly contracting hinder region of the body, a, nucleus ; b, contractile vacuole, close to the pharynx. 28. The same devoid of flagella. a, nucleus ; c, c, the two dark pigment spots (so-called eyes) near the mouth. 29. Oikomonas termo (ilonav t -rmo) Ehr. ; one of the Monadidea. a, nucleus ; b, contractile vacuole ; c, food-ingesting vacuole ; d, food-particle, x 440. 30. The food-particle d has now been ingested by the vacuole. 31. Oikomonas mutabilis, Kent (Monadidea), with adherent stalk, a, nucleus ; b, contractile vacuole ; c, food-particle in food vacuole. 32, 33. Cerco- monas craxsicauda, Duj. (Monadidea), showing two conditions of the pseudopodium-protruding tail, a, nucleus ; b, contractile vacuoles ; c, mouth. Fani. 5. HETERCMONADINA, Butschli. Small colourless or green monads which possess, besides one chief flagellum, one or two smaller paraflagella attached near it, often forming colonies secreting a co. union stalk. Genera. Monas (Ehr.), Stein; Dcndromonas. Stein; Cephalo- tli minium, Stein ; Anthophysa, Bory d. Vine. (Fig. XXL 12, 13); Dinobnion, Elir. (Fig. XX. Sand 15); Epipyxis, Ehr.; Uroglena, Ehr. (Fig. XX. 5). ORDER 2. EUGLENOIDEA, Butschli. Characters. Generally somewhat large and highly developed monoilagellate forms, of monaxonic or slightly asymmetrical build. Cuticle present ; cortical substance firm, contractile, and elastic ; some forms quite s.tiff, others capable of definite annular contraction and worm-like elongation. At the base of the flagellum a small or large mouth leading into a more or less distinct pharyngeal tube. Near this is always the contractile vacuole. Rarely a pair of flagella instead of one. Fain. 1. COZLOMONADINA. Coloured Euglenoidea, with numer ous small chlorophyll corpuscles or 1 to 2 large plate-like green or brown chromatophors. Mouth and pharynx inconspicuous ; nutri tion probably largely vegetal (holophytic). Genera. Ccelomonas, Stein ; Gonyostomum, Dies. ; Vacuolaria, Cienk. ; Microglena, Ehr. ; Chromnlina, Cienk. ; Cryptoglena, Ehr. Fam. 2. EUGLENIXA, Stein. Body monaxonic, elongated, hinder end pointed. Spirally striated cuticle. A fine mouth-aperture leads into the well-developed tubular pharynx. Flagellum usually single, sometimes paired, often cast oil". Near the pharynx is the reservoir " of the contractile vacuoles and several of the latter. A single (sometimes two) stigma or colour-speck near the same spot. Chromatophors nearly always present, generally bright green. A large nucleus in the middle of the body. Multiplication by longitudinal fission. Encysted condition and attendant fission imperfectly studied. Copulation doubtful. Genera. () With flexible cuticle -.Euglena, Ehr. (Fig. XX. 13, 17 ; this is probably Priestley s "green matter," from which he obtained oxygen gas ; though one of the very commonest of all Protozoa, its life-history has yet to be worked out) ; Colacium, Ehr. ; Eutreptia, Perty. (b} With stiff, shell-like cuticle : Ascoglcna, Stein ; Trachclo- monas, Ehr. ; Lepodnclis, Perty ; Phacus, Nitzsch. Fam. 3. MEKOIDINA, Butschli. Similar to the Euglenina, but devoid of chlorophyll, a deficiency connected with the saprophytic mode of life. Stigma always absent. Genera. () With flexible cuticle : Astasiopsis, Butschli ; Asta- siodcs, Butschli. (b) With stiff cuticle and non-contractile body : Monoidium, Perty ; Atractonema, Stein ; Rhabdomonas, Fresenius. Fam. 4. PERANEMINA. Very contractile (metabolic) colourless Euglenoids. Mouth and pharynx large ; inception of solid nutri ment certainly observed. Genera. Peranema, Duj. (Fig. XX. 16); Urccolus, Meresch. Fam. 5. PKTALOMONADINA. Colourless, non-metabolic forms. Mouth opening at the base of the single large flagellum. Genera. Petalomonas, Stein. Fam. 6. ASTASINA. Colourless, metabolic, or stiif Euglenoids, differing from the rest in having a small or large paraflagellum in addition to the chief one. Nutrition partly saprophytic partly animal. Genera. Astasia, Ehr. emend. Stein (Fig. XX. 27, 28) ; Hetero- ncma, Duj. ; Zygoselmis, Duj. ; Sphcnomonas, Stein ; Tropido- scyphus, Stein. ORDER 3. HETEROMASTIGODA, Butschli. Characters. Small and large monads. Naked and even amoeboid or with stiff cuticle. Two flagella at the anterior end differing in size : the smaller directed forwards subserves the usual locomotor function ; the larger is directed backwards and trailed, without movement. Sometimes two backwardly directed flagella are present. Always a mouth and animal nutrition. Always colourless. Fam. 1. BODONINA, Butschli. Size of the two flagella not very different. Genera. Bodo, Ebb. emend. Stein (Fig. XX. 23 to 26, and Fig. XXI. 10 ; the hooked monad and the springing niODad of Dai- linger and Drysdale (66) ; Hcteromita of Dujardiu and Kent); Phyllomitus, Stein ; Cotyonema, Stein ; Dallinrjcria, Kent ; Tri- mastix, Kent. Fam. 2. ANISONEMINA, Kent. Large forms with cuticle ; differ ence of the two flagella considerable. Mouth, pharynx, and animal nutrition. Genera. Anisoncma, Duj. ; Entosiphon, Stein. ORDER 4. ISOMASTIGODA, Butschli. Characters. Small arid middle-sized forms of monaxonic rarely bilateral shape. Fore-end with 2, 4, or seldom 5 equal-sized and similar flagella. Some are coloured, some colourless ; naked 01- with strong cuticle or secreting an envelope. Mouth and pharynx seldom observed ; nutrition generally holophytic (i.e., like a green plant), but in some cases, nevertheless, holozoic (i.e., like a typical animal). Fain. 1. AMPHIMONADINA. Small, colourless, biflagellate Iso- mastigoda. Genera. Amphimonas, Duj. (? Pseudospora, Cienk.). Fam. 2. SPONGOMONADINA, Stein. Small colourless oval forms, with two closely contiguous flagella. Chief character in the union of numerous individuals in a common jelly or in branched gelatinous tubes, the end of each of which is inhabited by a single and distinct individual. Genera. Spongomonas, Stein ; Cladomonas, Stein ; Rhipido- monas, Stein. [Group Phytomastigoda, Butschli. The following three families, viz., Chrysomonadina, Chlamydomonadina, and Yolvocina, are so closely related to one another as to warrant their union as a sub order. They are typical Isomastigoda, but have chlorophyll corpuscles and holophytic nutrition with correlated deficient mouth and pharynx. They are usually regarded by botanists as belonging to the unicellular Alga?.] Fain. 3. CHRYSOMONADINA, Biitschli. Single or colony-forming ; seldom an envelope. Spherical free-swimming colonies may be formed by grouping of numerous individuals around a centre. With two or rarely one brown or greenish brown chromatophor; a stigma (eye-speck) at the base of the flagella. Genera. Stylochrysalis, Stein; Ohrysopi/xis, Stein; Nephroscl- mis, Stein ; Synura, Ehr. ; Syncrypta, Ehr. (Fig. XX. 4). Fam. 4. CHLAMYDOMONADINA. Fore-end of the body with two or four (seldom five) flagella. Almost always green in consequence of the presence of a very large single chromatophor. Generally a delicate shell-like envelope of membranous consistence. 1 to 2 contractile vacuoles at the base of the flagella. Usually one eye- speck. Division of the protoplasm within the envelope may pro duce four, eight, or more new individuals. This may occur in the swimming or in a resting stage. Also by more continuous fission microgonidia of various sizes are formed. Copulation is frequent. Genera. Hymcnomonas, Stein; Chlorangium, Stein; Chloro- gonium, Ehr. (Fig. XX. 6, 7) ; Polytoma, Ehr. ; Chlamydomonas, Ehr. (Fig. XX. 1, 2, 3); H&matococcus, Agardh ( = Chlamydo- coccus, A. Braun, Stein ; Protococcus, Colin, Huxley and Martin ; Chlamydomonas, Cienkowski) ; Carteria, Diesing ; Spondylomorum, Ehr. ; Coccomonas, Stein ; Phacotiis, Perty. Fam. 5. VOLVOCINA. Colony-building Phytomastigoda, the cell- individuals standing in structure between Chlamydomonas and Hamiatococcus, and always biflagellate. The number of individuals united to form a colony varies very much, as does the shape of the colony. Reproduction by the continuous division of all or of only certain individuals of the colony, resulting in the production of a daughter colony (from each such individual). In some, probably in all, at certain times copulation of the individuals of distinct sexual colonies takes place, without or with a differentiation of the colonies and of the copulating cells as male and female. The result of the copulation is a resting zygospore (also called zygote cr oo-spermospore or fertilized egg-cell), which after a time develops itself into one or more new colonies. Genera. Gonium, 0. F. Mu ller (Fig. XX. 14) ; Stephanosph&ra, Colin ; Pandorina, Bory de Vine. ; Eudorina, Ehr. ; I olmx, Ehr. (Fig. XX. 18, 20). [The sexual reproduction of the colonies of the A olvocina is die of the most important phenomena presented by the Protozoa. In some families of Flagellata full-grown individuals become amoeboid, fuse, encyst, and then break up into flagellate spores which develop
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