REPRODUCTION 



183 



Among vertebrates the famed axolotl, Amhy stoma tigrinum or tiger 

 salamander, under certain conditions attains sexual maturity and breeds 

 while it is still in the larval form. In some of the Mexican lakes this is 



Fig. 140. — Stages in the life history of the liver fiuke, Fasciola hepatica. The scale of 

 enlargement is not the same for the several figures, a, egg with the ciliated larva (mir- 

 acidium) ; b, miracidium or ciliated larva emerged from egg; c, sporocyst producing redia3 

 (r) within itself; d, a redia producing cercarise; e, cercaria emerged from redia; /, cercaria 

 which has lost its tail and has encysted; g, adult liver fluke (outline only). {From Leuckart- 

 Nitsche Wall Chart.) 



Fig. 141. — The origin of parthenogenetic ova in the redia of Cercaria Jiabelliformis. 



A, lower end of redia with developing parthenogenetic ova, some in process of maturation; 



B, much magnified parthenogenetic ovum with polar body, ovum and polar body prepar- 

 ing to divide; ph, polar body. (From Faust in University of Illinois Biological Monographs.) 



said to be the usual occurrence. In Kansas and Nebraska this method of 

 reproduction in Amby stoma tigrinum has been observed but rarely, while 

 in many locahties it probably does not occur at all. 



