ACINETARIA. 53 



the nucleus, are formed, and eventually nipped off as free-swimming 

 ciliated forms. 



3. Internal budding is the most common method of increase. It 

 takes place in Tdkophrya quadripartita as follows : a funnel-shaped 

 invagination of the apical surface is formed, the opening of which 

 narrows to a pore. The bud arises from the base of the pit or 

 brood-pouch so formed, as a projection containing a part of the 

 nucleus. Eventually the bud becomes constricted off so as to lie 

 freely in the brood-pouch, accpuires some cilia, and escapes through 

 the opening as the free-swimming young form. In Dendrocometes 

 the bud is evaginated through the pore before separation, so that it 

 forms a projection of the body of the mother. The young are 

 always ciliated, and the ciliation may be holotrichous, hypotrichous, 

 or peritrichous. It occasionally happens (PoJoplinja fixa, etc.) that 

 a whole individual retracts its tentacles, acquires cilia, and breaks 

 away as a free-swimming swarmer. 



Conjugation of the temporary kind has been observed, and is 

 probably a general phenomenon in the group. The changes of the 

 macro- and micronucleus accompanying it seem to be of the same 

 nature as in the Ciliata. 



Encystment is of common occurrence, but its relation to other 

 vital phenomena is not known. The cyst wall often possesses 

 annular thickenings. 



Fam. 1. Hypocomina. Freely movable, not attached ; with permanently 

 ciliated ventral surface and one suctorial tentacle. Hypocoma Gruber, m., 

 ectopar. on Zoothamnium. 



Fam. 2. Urnulina. AVith one or two (rarely more) tentacles not distinctly 

 knobbed, llhynchcta Zenker, freely motile, without theca, on ventral side of 

 Cyclops ; Urnula Clap, and L., attached and with theca, on stalk of Epistylis. 



Fain. 3. Metacinetina. With stalked funnel-shaped theca, the walls of 

 which are perforated by slits for the exit of the knobbed tentacles. Metacinetu 

 Butschli, f.w. 



Fam. 4. Podophryina. Tentacles numerous and usually considerable, on the 

 whole surface or only apical, either all distinctly knobbed, or some of them 

 without knobs serving as prehensile tentacles. Spwrophrya Clap, and L., 

 without stalk, endoparasitic in Ciliata; Endosphxra Engelm., Podophrya Ehrb , 

 stalked, with knobbed similar tentacles from all parts of body ; Ephelota 

 Wright (Fig. 44), tentacles both knobbed and pointed, chiefly from free end, 

 m., on Hydroids, Polyzoa, and Crustacea; Podocyathus Kent, like the last, but 

 with theca. 



Fam. 5. Acinetina. Stalked, or with stalked or unstalked theca with 

 simple opening. Tentacles numerous, all alike, and usually distinctly knobbed. 

 Tokophrya Butschli ; Acineta Ehrb. (Fig. 43). stalk continued as theca ; Soleno- 

 phrya Clap, and L., theca sessile. 



Fam. 6. Dendrosomina. Without stalk or theca. Tentacles numerous, all 



