1895 THE MICHOSCOPE. 151 



scissors in one week there will be three complete hydra. 

 When a hydra is cut in two transversly and longitudi- 

 nally, at the end of eight days there w^ill be eight hydra. 

 Several pieces of the same animal can h'ri made to grow 

 together and also pieces of several different animals . 



It is quite difficult to perform the preceding experi 

 ment by uniting the green with the brown hydra. 



Reproduction is produced by budding and by eggs. 

 When the animal is well nourished the food produces 

 little hollow buds which communicate with the digestive 

 cavity of the mother. At the end of two days in sum- 

 mer and six weeks in winter this little bud is detached 

 and becomes a separate animal. The hydra does not 

 usually carry more than five buds at the same time, these 

 being in different stages of development. But in arti- 

 ficial culture with a high temperature and plenty of food 

 more are produced and they remain attached to the 

 mother a longer time. Tremblayhad a gray hydra which 

 carried nineteen little ones which belouged to three gen- 

 erations. 



The fresh water hydra will not form a new individual 

 from a tentacle, although some salt water species can be 

 made to do so. Sexual generation is produced by fecun- 

 dated eggs. Toward the last of the summer the foot 

 produces some protuberances which at first resemble 

 buds but instead of producing either a mouth or ten- 

 lacles they form in their cavity either ovules or sperma- 

 tozoa. These external organs should be considered as 

 being true individuals charged exclusively with the 

 care of reproduction, as it is often the case with marine 

 polyps. 



PERSONAL. 



Herbert M. Hill is city chemist of the Department of 

 Health of the city of Buffalo, N. Y. 



