54 



PLATYHELMINTHES TREMATODA 



placed on the dorsal surface. Each sac is a single cell, and 

 within it not one merely, but several "flames," or bunches of 

 rhythmically contractile cilia, are present. These are placed on 

 the course of excessively fine canals, which perforate the proto- 

 plasm of this cell. The terminal branches of the excretory canals 

 end in branched cells, apparently devoid of " flames." 



The reproductive system is very similar to that of certain 



4-dn 



FIG. 20. Temnocephala novae-zecdandiae FIG. 21. The same from the dorsal surface, 



Has. x 10. Ventral view to show the to show the excretory system (double 



digestive and reproductive systems. line), and the nervous system (black 



(After Haswell.) and shaded). (After Haswell.) 



d, Intestine ; din, dorso-lateral nerve ; dn, dorsal nerve ; ez.o, excretory aperture on 



dorsal surface ; ex.s, terminal excretory sac ; m, mouth ; ov, ovary ; ovd, oviduct ; 



ph, pharynx ; rh, rhabdites ; rh.c, cells in which the rhabdites are formed ; rv, yolk 



receptacle ; sc, sucker ; sh, shell-gland ; te, testes ; ut, uterus ; vg, vagina ; vn, 



ventral nerve ; vs, vesicula semiualis ; yd, yolk-duct ; yg, yolk-gland. ?, <J, common 



genital pore. 



Rhabdocoels. An armed penis and the female genital duct 

 open into a genital atrium, and this by a single aperture 

 (?,<?, Fig. 20) to the exterior. The fertilised ovum and yolk 

 are enclosed in a stalked shell formed in the uterus. 



The interest and importance of the Temnocephalidae lies in 

 the fact that they are almost as much Turbellaria as Trematodes. 



