172 



Heredity. 



species. In these two species the females were much 

 alike, while the males were not only yery different from 

 the females, but also from each other. 



Fig. 1. Toung female Rotifer. 

 Hydatiaa senta. a. cloaca. 6. 

 contractile vesicle c. water 

 tubes, d. stomach, e. ovary. 

 /. ganglia, g. stomach, i. mouth- 

 parts. 



Fig. 2. Male of the same species. 

 a. orifice of penis, b. contractile 

 vesicle, c. testes, d. ganglion. 

 e. setigerous apparatus. 



Since the year 1855 the subject has been studied by 

 many naturalists, and the males have been found in 

 such a number of species that it is probable that the 



