460 



THE PROTOZOA 



;points of the primitive transverse plane. In such a type the zones of cilia 

 run obliquely along the sides of the body, or may be confined to the ventral 

 surface, where they run a more or less elliptical course round the sucker, 

 thus producing the hypotrichous type seen in Ephelota gemmipara and in the 

 persistent larval form Hypocoma acinetarum. Examples of holotrichous 

 larvae are seen in Tocophrya limbata and Urnula epistylidis (Hickson and 

 Wadsworth, 886). In all cases the principal or dorsiventral axis of the larva 

 becomes the principal axis of the adult ; in the process of budding, however, 

 the principal axis of the bud arises at right angles to that of the parent, accord- 

 ing to Collin ; Filipjev, however, does not confirm this for Tocophrya quadri- 

 partita. 



The remarkable form Tachyblaston described by Martin lives in the adult 

 condition attached to the stalk of Ephelota; it produces buds each with a 

 single tentacle, which creep up the stalk of the Ephelota and penetrate into 

 the body, becoming parasitic in it and multiplying by fission to produce 

 ciliated larvae, which in their turn swim out, attach themselves to the stalk 

 of the Ephelota, and become adult forms. 



The conjugation of the Acinetaria conforms in general to the 

 type of the process seen in Ciliata, as regards cytological details. 

 Conjugation may take place between two individuals fixed near 



FIG. 193. Free-swimming larva of Dendrosoma radians. A, Side view ; B, viewed 

 from above ; C, older larva with the first rudiments of the tentacles beginning 

 to appear. After Hickson and Wadsworth (886). 



together (Fig. 190, G) ; then a lobe or outgrowth may be formed 

 from one individual, which meets a similar outgrowth from the 

 other, thus establishing contact. On the other hand, as in Peri- 

 tricha, conjugation may take place between a fixed, ordinary indi- 

 vidual and a free-swimming bud or larva liberated from another 

 adult individual (Martin ; Collin, 879). In Dendrocometes the 

 macronuclei come into contact during conjugation, but separate 

 again (Hickson and Wadsworth). 



Classification. The Acinetaria are divisible into eight families (cf. 

 Doflein, 7). 



1. Hypocomidce, for the single, somewhat aberrant genus Hypocoma, which 

 is free-swimming, ciliated on one surface, and with a single suctorial tentacle 

 possibly a persistent larval form (see Collin, 877). 



2. Urnulidce. With or without a house, with one or few tentacles. Rhyn- 

 cheta, Urnula (Fig. 191). 



3. Metacinetidce. With a stalked house opening at the upper end for the 

 exit of the tentacles. Metacineta. 



