SECT, vn 



PHYLUM TROCHELMINTHES 



325 



depression on the dorsal surface and places in position one by one. 

 The pellets are usually formed of foreign particles, but in some 

 species are made of the animal's own faeces. 



The ciliation of the trochal disc is subject to considerable 

 variation. In its simplest form the disc is surrounded by a single 



II 



S.Hexarhhra 



3-Troch o sjjhaera 



FIG. 275. Typical forms of Rotifera. In 1, A shows the outer form, B the muscular system . 

 a. anus ; br. brain ; c 1 c 2 . ciliary circlets ; cl. cloaca ; d. gf. digestive gland ; d. I. dorsal 

 limb ; e. eye-spot ; I. I., I. I', lateral limbs ; m, muscles ; mth, mouth ; nph. nephridial 

 tube ; ov. ovary ; ph. pharynx ; s. sense-organ ; i\ L ventral limb. (After Hudson and 

 Gosse (1 and 2) and Korschelt and Heider (3).) 



circlet of cilia, within which lies the mouth. A modification of 

 this type may be produced by the prolongation of the ciliary 

 crown into long arm-like processes fringed with cilia, as in 

 Stephanoceros (2), or, as in Floscularia (1), into blunt elevations 



