THE DEVELOPMENT OF HYDRA. 2J\ 



in this particular locality conditions were antagonistic to the de- 

 velopment of sexual organs, but favorable for budding. After 

 the hydras were brought into the laboratory and put in aquaria 

 with abundance of food and the water kept well aerated, they re- 

 produced by budding more rapidly than out of doors. As many 

 as four and sometimes five buds were found on the same individual. 

 After the hydras continued to bud very vigorously from two to 

 six weeks, ovaries and spermaries were produced. Buds and 

 ovaries or spermaries are often contemporaneous on the same 

 individual. Sexual organs were never found on the buds. But 

 if the buds after becoming mature were supplied with plenty of 

 food, they in turn would produce sexual organs after passing 

 through a stage of vigorous budding, as described above. The 

 time for the appearance of the sexual organs on different individ- 

 uals varied with the rate of budding. 



According to Downing when buds and spermaries were found 

 on the same individual, the spermaries appeared on the vigorous 

 bud. 



The hydra in most instances continued to feed during sexual 

 reproduction. The endodermal cells at the time of the first 

 formation of the sexual organs are gorged with food and proto- 

 plasmic granules, while the ectodermal cells are less granular and 

 begin to show vacuoles. During the early formation of the 

 sexual organs the endodermal cells, especially in the region of 

 the sexual organs, become less granular and are almost free 

 from food granules. This condition is most striking while the 

 pseudopodia of the egg are forming. The pseudopodia grow so 

 rapidly that the digestive process can not keep pace. But when 

 the pseudopodia are completely drawn in, the endodermal cells 

 immediately ingest food and show their former granular condi- 

 tion. But in those hydras that cease feeding during the sexual 

 period, the endodermal cells remain non-granular and large 

 vacuoles appear. The size of the egg in Hydra sp.? varies con- 

 siderably with the amount of food present. This condition indi- 

 cates a rapid use of the nutritive material during the development 

 of the ovum. 



Hydras that were kept in aquaria in a starved condition never 

 produced sexual organs and very seldom budded. The ecto- 



