ROTATORIA 



259 



incomplete form of the male begin only after the trochal 

 organ and the foot have been formed.^ 



General Considerations. 



The development of the Rotatoria gives us as yet no 

 information as to their doubtful position in the system. 

 Such forms as that of Trochosphaera cequatorialis (Fig. 

 116), found by Semper in the Philippines, point with 

 almost imperative force to relationships with the Tro- 



C'e^ -^ 



Fig. 116.— Ti-oc7iosp?icpi-a aquatorialis (after Sempeb). Ce, cloaca; Dv, appendi- 

 cular Klands of the fore-gut; Ex, duct of the excretory organs; 6, brain; Ge, 

 female sexual organs with duct ; M, mouth ; Mu, musculature ; N, nerve that 

 emerges from the brain ; S, oesophagus ; Si, sense organ ; W„ preoral, W„, post-oral, 

 ciliated band. 



chophore larva of the Annelida (comp. p. 266). Like the 

 latter, Trochosphcpra possesses a complete preoral circle of 

 cilia and an indication of a post-oral one. Both of these 

 are also to be recognized in the trochal organ of other 

 Rotatoria, the form of which is different from that of the 

 Trochophore. The course of the intestine is similar to that 

 of the annelid Trochophore. The structure of the excretory 

 system also argues for a relationship with the Trochophore- 

 like forms. The excretory canals of the Rotatoria begin 

 with blind ciliated funnels in the body cavity, and the same 



1 [Our knowledge of the development of the Eotatoria has recently- 

 been much enlarged by the thorough investigation of Zelinka, to which 

 the reader is referred (see Appendix to Literature on Rotatoria).— K.] 



