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 



Fig. 20. Temnocephala novae-zealandiae 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 ; ex.o, excretory aperture on 



dorsal surface ; ex.s, terminal excretory sac ; in, 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 seminalis ; yd, yolk-duct ; yg, yolk-gland. 9,6, common 



genital pore. 



Ehabdocoels. An armed penis and the female genital duct 

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

 ($,c, 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. 





