VII 



PHYLUM TROCHELMINTHES 



307 



or may be interrupted as in Brachionus, in which the proe-oral 

 circlet is represented by three distinct lobes, or as in Pedalion. 

 in which both circlets are divided into right and left moieties. 

 In one genus the trochal disc is absent. 



m. 



S.Hexar^hra 



3-Troch o s > h a e r a 



Fia. 250. Typical forms of Rot if era. In ^ a shows the outer form, 6 the muscular system. 



ft. anus ; bi: brain : c 1 . t-. ciliary circlets ; cl. cloaca ; </. ril. digestive gland ; it. /. dorsal limb ; 

 i. eye-spot; 1. I., I. I', lateral limbs; m. muscles; uti/i, nephridial tube; or. ovary ; jili. 

 pharynx ; s. sense organ ; c. I. ventral limb. (After Hudson and Gosse (1 and '2) and 

 Korschelt and Heider (3).) 



Digestive Organs. The typical form of mastax or pharyngeal 

 mill is that described in Brachionus (Fig. 246). There is an un- 

 paired incus consisting of a short stem or fulcrum (/), and of t\\n 

 broad branches or rami (r), and a pair of m" I Id, each consisting 



x 2 



