32 



PROTOZOA 



flagellata and the Rhynchoflagellata with the true Flagellata in one 

 class. But the peculiarities of the organization of the two former 

 groups is best emphasized by treating them as separate classes de- 

 rived from the Flagellata. Neither group leads on to the Ciliata or 

 to any other group, but they must be regarded as forming a lateral 

 branch of the family tree of "Corticata. The relationship of Nocti- 

 luca to Peridinium was first insisted upon by Allman, but has quite 

 recently been put in a new light by Biitschli, who identifies the 

 atrial recess of Noctiluca (Fig. XXII. 20, 6) with the longitudinal 

 furrow or groove of the Dinoflagellata, and the large and minute 

 flagella of the former with the transverse and longitudinal flagella 

 respectively of the latter. The superficial ridge c of Noctiluca 

 appears to represent the continuation of the longitudinal groove. 



The phosphorescence of the sea, especially on northern coasts, is 

 largely caused by Noctiluca, but by no means exclusively, since 

 Medusre, Crustaceans, Annelids, and various Protozoa often take part 

 in the phenomenon. Not unfrequently, however, the phosphor- 

 escence on the British coasts seems to be solely due to Noetiluca, 

 which then occurs in millions in the littoral waters. 



FIG. XXIII. Ciliata. i. Bpiroitomum ambiguum, Ehr.; one of the Hetero- 

 , tricha; x 120. Observe on the right side the oral groove and special hetero- 



trichous band of long cilin. ft, moniliform nucleus ; b, contractile vacuole. 



2. Stentor polymorphic, Miiller ; one of the Heterotricha ; x 50 ; group of 



individuals with the area fringed by the heterotrichous cilia expanded 

 trumpet-wise. 3. Tintinnns lagenula, C. and L. ; one of the Hetero 



tricha; x 300. 4. Strombidium Claparedii, S. K.; one of the Peritricha; 

 x 200. 5. Empty shell of Codonella campanella, Haeck.; one of the 



Heterotricha ; x 180. 6, 7. Torquatella typica, Lankester. p, the supra- 

 oral lobe seen through the membranous collar. 8, 9. View of the 

 base and of the side of Trichodina pediculus, Ehr.; one of the Peritricha; 

 x 300. a, nucleus ; c, corneous collar ; d, mouth. 10. Sjiirochona 

 gemmipara, Stein ; one of the Peritricha ; x 350. a, nucleus ; g, bud. 11. 

 Vorticella citrina, Ehr.; x 150 (Peritricha). At d multiple fission of an 

 individual cell to form "microgonidia." 12. Vorticella -uricrostoma, 

 -Ehr. (Peritricha); x 300. At e eight "microgonidia" formed by fission 

 of a single normal individual. 13. Same species, binary fission, a, 

 elongated nucleus. 14. Vorticella nebidifira, Ehr. ; free-swimming 

 zooid resulting from fission in the act of detaching itself and swimming 

 away, possessing a posterior circlet of cilia, e, ciliated disk ; /, 

 pharynx. 15. Vorticella mtcrostoma, Ehr.; normal zooid with two 

 microgonidia (or microzooids) c,d, in the act of conjugation, o, nucleus ; 

 6, contractile vacuole ; e, ciliated disk ; /, pharynx. 16, Vorticella 

 microstoma, Ehr., with stalk contracted and body enclosed in a cyst, a, 

 nucleus. 17. Vorticella ncbitli/fra, Ehr. a, nucleus ; 6, contractile 

 vacuole ; c, 'muscular region of the body continuous with the muscle of the 

 stalk ; rf, pharynx (the basal continuation of the oral vestibule which 

 receives at a higher point the fcecal excreta and the ejected liquid from 

 the contractile vacuole). 18. Carchesittm spectabile, Ehr. ; retractile 

 colony; X 50. 19 Trichocysts of Epistylis Jlavicans, Ehr., as figured 

 by Greeff. 20. Opercularia stenostoma, Stein ; x 200 ; a small colony. 

 Observe the ciliation of the oral vestibule and the upstanding ciliate disk 

 (opercular-like). 21, 22. Pyzicola affinis, S. K.; one of the stalked 

 loricate Peritricha, in expanded and retracted states, x, the true oper- 

 culum. 23, 24. Gyrocoris oxyura, Stein ; one of the free-swimming 

 Peritricha, with spiral equatorial cilia-band ; x 250. b, contractile 

 vacuole. 25, 26. Ttiuricola valvata, Str. AVright ; one of the sessile 

 tubicolous Peritricha. Two individuals are as a result of fission tempo- 

 rarily occupying one tube ; tt, the valve attached to the tube, like the door 

 of the trap-door spider's nest and the valve of the Gasteropod Clausilium. 



CLASS V. CILIATA, Ehrenherg (Infusoria seusu stricto). 



Characters. Corticata of relatively large size, provided with 

 either a single band of cilia surrounding the anteriorly placed oral 

 aperture or with cilia disposed more numerously over the whole 

 surface of the body. The cilia are distinguished from the flagella 

 of Flagellata by their smaller size and simple movements of 

 alternate flexion and erection ; they serve always at some period of 

 growth as locomotor organs, and also very usually as organs for 

 the introduction of food particles into the mouth. Besides one 

 larger oblong nucleus a second (the paranucleus) is invariably (?) 

 present (Fig. XXV. 2), or the nucleus may be dispersed in small 

 fragments. Conjugation of equal-sized individuals, not resulting 

 in permanent fusion, is frequent. The conjugated animals separate 

 and their nuclei and paranuclei undergo peculiar changes ; but no 

 formation of spores, either at this or other periods, lias been de- 

 cisively observed (Fig. XXV. 8 to 15). Multiplication by transverse 

 fission is invariably observed in full-grown individuals (Fig. XXV. 

 16), and conjugation appears to take place merely as an interlude 

 in the fissiparous process ; consequently young or small Ciliata are 

 (with few exceptions) unknown. Possibly spore-formation may 

 hereafter be found to occur at rare intervals more generally than is 

 at present supposed (Fig. XXIV. 15, 18). A production of micro- 

 gonidia by rapid fission occurs in some Peritricha (Fig. XXIII. 

 11, 12, 14, 15), the liberated microgonidia conjugating with the 

 normal individuals, which also can conjugate with one another. 



The Ciliata, with rare exceptions (parasites), possess one or more 

 contractile vacuoles (Fig. XXV. 3). They always possess a delicate 

 cuticle and a body-wall which, although constant, in form is elastic. 

 They may be naked and free-swimming, or they may form horny 

 (Fig. XXIII. 21, 25) or siliceous cup-like shells or gelatinous 

 envelopes, and may be stalked and form colonies like those of 

 Choanoflagellata, sometimes with organic connexion of the con- 

 stituent units of the colony by a branching muscular cord (Vorti- 

 cellidoe). Many are parasitic in higher animals, and of these some 

 are mouthless. All are holozoic in their nutrition, though some are 

 said to combine with this sapropliytic and holophytic nutrition. 



The Ciliata are divisible into four orders according to the 

 distribution and character of their cilia. The lowest group (the 

 Peritricha) may possibly be connected through some of its members, 

 such as Strombidium (Fig. XXIII. 4), with the Flagellata through 

 such a form as Lophomonas (Fig. XXI. 9). 



In the following synopsis, chiefly derived from Saville Kent's 

 valuable treatise (71), the characters of the families and the names 

 of genera are not given at length owing to the limitation of our 

 space. 



ORDER 1. PEKITRICHA, Stein (79). 



Characters. Ciliata with the cilia arranged in one anterior 

 circlet or in two, an anterior and a posterior ; the general surface of 

 the body is destitute of cilia. 



Sub-order 1. NATANTIA (animals never attached). 



Fam. 1. TOKQUATELLID.E. 



Genns. Torquatclla, Lankester, like Slrombidium, but the^cilia 

 adherent so as to form a vibratile membranous collar (Fig. XXIII. 

 6, 7). 



Fam. 2. DICTYOCYSTID.E. Animals loricate. 



Fam. 3. ACTINOBOLIIXE. Illoricate, with retractile tentacula. 



