Il6 THE INVERTEBRATA 



the other. It is not known what happens to the two zygote nuclei in 

 these cases. 



The arrangement of the larval cilia in rings, the prevalence of a 

 sessile habit, the frequent inequality of conjugants, and sometimes 

 the absorption of one of these by its partner, suggest the derivation of 

 this subclass from a form which resembled the Peritricha. 



Sphaerophrya (Fig. 87 F, F'). Spherical species; which are at first 

 free and provided with knobbed tentacles on all sides ; afterwards be- 

 come endoparasites in ciliates ; and are then without tentacles. Fission 

 equal or somewhat unequal ; in the parasitic stage it is repeated before 

 the young escape. Parasitic in Paramecium^ etc. 



Ephelota (Fig. 96). Stalked; not seated in a cup; bearing tentacles 

 distally. Reproduction by external, usually multiple, budding. 

 Marine. 



Acineta (Fig. i). Stalked; the stalk expanding to form a shallow 

 cup. Reproduction by internal budding. In fresh waters and marine. 



Dendrocometes (Fig. 87 G). Body lens-shaped; without stalk; with 

 branched arms which end in several pointed tentacles. Reproduction 

 by formation of one internal bud. Sessile upon the gills of Gammarus. 



