THE REACTION OF HYDRA TO INANITION. 175 



in this case no effort to free the ingested tentacle. After twenty 

 minutes, however, the tentacle was seen to be slipping out of the 

 mouth. When freed the tentacle presented a constricted zone 

 about which the peristome had held it during the period of 

 ingestion. 



The history of this tentacle has an interesting bearing upon our 

 observations; for it shows that the tentacle was not one that 

 had undergone necrosis prior to its having been ingested, since 

 it showed no eroded tissue and eventually fully recovered, leaving 

 no trace of the constricted region. This tentacle, therefore, had 

 not suffered necrosis before being ingested. Marshall ('23) makes 

 this observation: "Some brown Hydras were induced to swallow 

 pieces of Hydra viridis by slipping the latter inside the carapace 

 of Daphnia, but they were ejected along with the remains of 

 food," p. 614. The suggestion may be taken that only dead 

 Hydra-tissue might be freely ingested since Marshall, in this case, 

 saw fresh Hydra tissue "ejected along with the remains of food." 



But our observations do not lend support to this negative 

 inference. Miss Edna McNally in 1923 observed an Hydra 

 viridis "put the end of one of its tentacles into its mouth." The 

 end of the tentacle could be clearly seen inside of the coel- 

 enteron. After the tentacle had been kept in the ccelenteron 

 about fifteen or twenty minutes, the Hydra dragged the shortened 

 tentacle with a ragged end from the mouth, leaving part of it 

 within the ccelenteron. 



In addition to having actually seen an Hydra ingest a piece 

 of its tentacle, we have observed a green specimen, which during 

 sustained inanition had but recently lost parts of some of its 

 tentacles, throw out from its mouth defragmented tissue of green 

 Hydra. On one occasion, after such cellular material had been 

 regurgitated, it was again ingested. 



Thus, actual observation of living individuals has yielded 

 evidence that Hydras, that have been deprived of food, feed upon 

 their tentacles. 



Further evidence was secured through isolating two series of 

 individuals. By depriving one of these series of food and feeding 

 the other series well, we have secured some interesting results. 



On March 14, 1925, six individuals were isolated in six watch 



