44 



DEVEL9PMENT OF CESTODES. 



each side of the proglottides. "We thus see that although each 

 segment is sexually distinct and iadependent, and that the 

 segments can live a free life for a time, yet they are all united 

 into one animal by the nervous and excretory systems. 



Development of Cestodes. — The male organs reach maturity 

 before the female : as soon as they are ripe, copulation takes 

 place, and the receptacle of the female becomes fiUed with sperm, 

 and then the female organs mature. 



The ova when fertihsed pass into the uterus, which becomes 

 very distended, and the rest of the proglottis becomes absorbed, 



SCOLEX OF T^NIA SOLIUM AND PROGLOTTIS OF TAPEWORM. 



A, Scolex of Tcenia solvum, seen from front, e, Proglottis of Tapeworm, 

 s, Suckers; h, circle of hooks; No, nerve-chord; Wv, water-vascular system; Ov, 

 ovary; T, testes ; TK, vas deferens ; Fgr, vagina; Ut, uterus; K, vulva; P, penis. 



— in fact the whole segment is fiUed with eggs. In the uterus 

 the eggs in the last segment are said to become free embryos ; 

 but this the writer has failed to detect in the many species of 

 Tapeworm examined. The eggs are round or oval and small. 

 The shell of the egg may be composed of several thin membranes 

 or of a thick and strong capsule. The curious six- or four- 

 hooked embryo (fig. 12, b) may be seen in the most highly 

 developed ova. In one genus of Tapeworms, known as Both- 

 riocephalus, of which a species is found in the human being in 

 Switzerland and elsewhere, the development takes place in the 

 water, the embryo leaving the ovum as an oval ciliated larva. 



