242 D. D. WHITNEY. 



When green hydras are put into the glycerine solution the en- 

 doderm cells become larger. As the cells are closely packed to- 

 gether their expansion laterally is prevented. Consequently be- 

 coming larger they push out into the enteric cavity, becoming 

 several times as long as in the normal animals. Fig. 3 shows 

 the condition of the endoderm cells of a green hydra that had 

 been in the glycerine solution for one hour. Some of the cells 

 are about twice the length of those in normal hydras but other- 

 wise they seem to be similar. 



In Fig. 4 the endoderm cells are much longer and more narrow 

 than in the preceding case. This hydra had been in glycerine 

 solution for three hours. In Fig. 5 the endoderm cells are about 

 the same size as in Fig. 4 but the interior of the cells is filled with 

 a very fine granular substance and the green bodies are scattered 

 about in this substance especially in the distal two thirds of the 

 cells. Very few green bodies were seen near the free end of the 

 cells. This section was from a hydra that had been in the glyc- 

 erine solution for sixty hours. 



The condition ot the endoderm cells of hydras that were ren- 

 dered entirely colorless by being kept in the glycerine solution for 

 eighteen days or more, Fig. 6, differs only from the endoderm 

 cells of hydras that had been in the glycerine solution for sixty 

 hours in having no green bodies in the cells. 



Each endoderm cell doubles its size at least within an hour 

 after being put into the glycerine solution as is seen in Fig. 3. 

 As it remains longer in the solution it becomes extended until 

 it is ruptured and owing to the pressure of the adjacent cells ex- 

 trudes much of its contents into the enteric cavity. As soon as 

 there is an equilibrium of pressure the rupture quickly heals or 

 regenerates thus making the cell intact again. Soon after it is 

 whole it swells again until it is ruptured a second time and dis- 

 charges more of its contents, including the green bodies, into the 

 enteric cavity. This process is repeated as long as the animal is 

 kept in the glycerine solution and if kept too long until its death. 

 By this repeated process of the rupturing of each endoderm cell 

 and the discharge of its contents all the green bodies of each cell 

 are finally eliminated and the cells remain colorless. 



The green bodies have been seen being ejected through the 



