HYDRA VI1UDIS. 



313 



slender towards the lower extremity; tentacles (3-10, 

 shorter than the body. 



THE ovaries are developed in spring and summer (April to 



;^f 



r 





June or July), and also in the autumn. Ecker has re- 

 marked that the eggs produced in the early part of the 

 year run their course in the following summer, while those 

 produced in the autumn pass the winter without change. 

 The spermary and ovary are home on the same individual, 

 the former a little behind the tentacles, and the latter 

 towards the lower part of the body. In the present spe- 

 cies there seems to be usually only a single ovum. 



H. viridis was discovered by Trembley in 1740. 



Hab. Ponds and still waters ; very common. 



