FURTHER STUDIES ON THE ELIMINATION OF THE 



GREEN BODIES FROM THE ENDODERM 



CELLS OF HYDRA VIRIDIS. 



D. D. WHITNEY. 



In a recent paper I called attention to the fact that when green 

 hydras are kept in a 0.5 per cent, solution of glycerine for sev- 

 eral days they gradually lose their green color and become col- 

 orless.^ The green bodies were observed to be thrown out of 

 the enteric cavity through the mouth but it was not determined 

 how they became separated from the endoderm cells in which 

 they are contained. It was a matter of conjecture whether the 

 endoderm cells became detached from the walls of the enteric 

 cavity and carried the enclosed green bodies with them, subse- 

 quently disintegrating and liberating the green bodies in the en- 

 teric cavity, or whether the endoderm cells became ruptured and 

 let their contents flow into the enteric cavity and then out through 

 the mouth. 



A microscopical study of the endoderm cells of both the nor- 

 mal green hydras and the green hydras that had been in a 0.5 

 per cent, solution of glycerine from one hour to about three 

 weeks gave the following results : 



In the normal hydras the endoderm cells are about as long as 

 broad and each contains a large vacuole at its inner end. Nearly 

 all of the green bodies are at the base of the cells. Figs, i and 

 2 show respectively in a cross and a longitudinal section the con- 

 dition of the endoderm cells in green hydras that were starved 

 for fourteen days in clear water. Several which were starved 

 only thirty-six hours were sectioned but the endoderm cells did 

 not differ noticeably from those in the green hydras that were 

 starved for two weeks. The animals were allowed to remain 

 without food in order that the endoderm cells, free from food, 

 might be compared with those of animals that had been in the 

 glycerine solutions for the same length of time without food. 



1 Biological Bulletin, 1907, XIV. 



241 



