184 W. A. KEENER AND P. N. JESTER. 



EXPLANATION OF PLATE. 



FIG. i. Interlocking secreting (a) and epithelio-muscular (b) cells of the 

 endoderm. b bears a food vacuole (c) within which is a nematocyst that shows 

 little distortion. X 1500. 



FIG. 2. An epithelio-muscular cell of endoderm bearing a food vacuole (a) 

 within which is a nematocyst that shows advanced internal disintegration. X 1500. 



FIG. 3. An epithelio-muscular cell of endoderm with adjacent ectodermal cells. 

 A greatly broken down nematocyst within a food vacuole (a) is contrasted with a 

 nematocyst in the usual position within the ectoderm (6). X 1500. 



FIG. 4. One of the transverse sections of a tentacular fragment that lay in the 

 ccelenteron of a sectioned Hydra from which food had been withheld, (a) residia 

 of secreting endodermal cells; (b) residia of epithelio-muscular endodermal cells. 

 X 750. From H. L. Firebaugh's slide "No. 15. 34.7-85.8." 



FIG. 5. Series of free-hand outlines to indicate changes that had taken place in 

 an individual Hydra from which food had been withheld. 



FIG. 6. Series of camera-lucida outlines to indicate changes that had taken 

 place in an individual Hydra from which food had been withheld. 



