PLANARIA NIGRA. 29 



face of aquatic plants in vigorous vegeta- 

 tion ; and animal substances are likewise 

 voraciously consumed. 



The sexual union takes place with the 

 black planaria, though rarely to be witness- 

 ed ; nor had I complete conviction of the 

 fact before August 1812, notwithstanding- 

 preceding incidents had led to such an in- 

 ference. Long anterior to that period, I 

 knew that this species propagated by eggs, 

 which, for the most part, are laid by those 

 of larger size, and usually in the course of 

 autumn; but they may occasionally be 

 found throughout the year, or obtained in 

 winter by the more genial temperature of 

 an apartment. No external characteristic 

 distinguishes the male and female planaria, 

 if there be actually a difference of sex be- 

 tween them : that which is represented 

 here, produced an egg, which entitles it at 

 least to the character of female ; and what 

 I supposed the male, was probably not quite 

 so large. The egg is imbued by a yellow- 

 ish viscous matter, attaching it to any twig 



