iy8 XV. A. KEPNER AN T D P. N. JESTER. 



Specimen "369 2 a" had been isolated in a hanging drop 

 until it had lost its tentacles. The slide made from this specimen 

 bears a complete series of sections in which the shortened 

 tentacles show no erosion such as Amceba and other parasites 

 cause. Moreover, all of our slides show no dedifferentiation 

 processes. We have slides that show wound scars at the end of 

 tentacular stumps but in which the ectoderm is laid down as a 

 continuous sheet about the tip (Example "370 2"). 



But our histological evidence leads further to the conviction 

 that tentacle-material is ingested and digested. Mr. Looper, of 

 this laboratory, has two individuals sectioned, in one of which the 

 sections show a series of sections of three fragments of tentacles 

 lying within the ccelenteron, while the other shows but one 

 fragment of tentacle lying within the ccelenteron (Looper's slides 

 "2 ovum la," and "Hydra Ovum n "). 



The transverse sections of the tentacular fragments, that are 

 to be found in sections of polyps that have suffered inanition, 

 show a diploblastic pattern but present very poor detail. In 

 Fig. 4 we have a transverse section of an ingested tentacular 

 fragment. The region of the endodermal epithelio-muscular cells 

 is most greatly broken down (Fig. 4, b). What we take to be 

 residia of secreting endodermal cells are indicated at a. The 

 ectoderm seems to be least attacked by the digestive fluids of the 

 ccelenteron. All elements here, too, have been greatly shrunken. 



Not only do the histological specimens show the tentacular 

 fragments lying within the ccelenteron but they indicate that the 

 material, thus taken in, is digested and absorbed. 



This was further checked by fixing specimens by the pond in 

 which a vigorous population of Hydras was growing and con- 

 trasting the histology of these with that of the isolated specimens 

 that had been kept under daily observation in the laboratory. 

 Slides, bearing material taken from the vigorous population of a 

 pond, show no Hydra-tissue within the ccelenteron and very few, if 

 any, nematocysts within the epithelio-muscular cells of the 

 endoderm. In contrast to this, the histology of specimen "375" 

 is significant. This specimen was isolated in a Petri dish, 

 containing spring water, at 3:30 P.M., October 28, 1921. At 

 9:25 A.M. the next day it was found to have had but the merest 



