Ill 



PLATODES SEXUAL ORGANS 



159 



glands open either into the outer copulatory apparatus, or into a 

 special fold of the same into which eggs and yolk are conducted, and 

 which will here be called the uterus. In the A coda and Alloiocoda 

 no definite connection between the germ glands and the copulatory 

 apparatus can be demonstrated. The sexual products here make their 

 way through the parenchyma to the copulatory apparatus. 



In the Trematoda (Fig. 114) an oviduct proceeding from the 

 ovarium is found, then two yolk ducts (dg) which collect the yolk from 

 the two lateral vitellaria. The oviduct and the yolk ducts together 

 enter an unpaired canal which we shall call egg passage. This passage 

 falls into 2 parts one small part at the beginning, the ootype, into 

 which the 3 ducts mentioned enter, and a long, generally coiled 



FIG. 115. Sexual organs of Taenia saginata 

 (medio-canellata), after Sommer. h, Testes ; vd, 

 vasa deferentia ; cb, cirrus pouch ; gp, genital pore ; 

 ov, oviduct ; ks, germaria ; sd, shell glands ; ds, 

 vitellarium ; u, uterus. 



FIG. 116. Fully ripe proglottides 

 (segments). A, Of Taenia saginata ; 

 B, of Taenia solium.' The dendriform 

 figure represents the uterus. 



portion, the uterus (u) t leading from the ootype to the female genital 

 aperture. The ootype receives the efferent ducts of the shell glands. 

 Fertilisation takes place here, and also the union of the yolk with the 

 egg ; and here a shell is formed round the fertilised egg. The ootype 

 has an exit either in the dorsal or the ventral surface of the body 

 through one more canal, Laurer's canal (Lg\ through which, probably, 

 in copulation, the sperm reaches the ootype from outside. The fertil- 

 ised eggs pass from the ootype into the uterus, where they often 

 collect in enormous numbers, at least in the Distomidce. The uterus 

 in these animals is consequently very long, and runs to the female 

 copulatory apparatus in numerous coils, which in the adult often 

 fill the greater part of the body. 



The Cestoda (Fig. 115) are closely allied to the Trematoda, especi- 

 ally in forms in which, as in Bothriocephalus, the sexual apertures lie 

 on one of the surfaces, and in which there are 2 lateral vitellaria. 

 The collecting passages of the vitellaria unite in such forms into 



