DIFFERENTIAL INHIBITION IN OBELIA 



485 



Presumably the large cells are encloderm cells which still 

 retain the phagocytic properties iiornially associated with 

 intracellular digestion. 



Occasionally we have noticed in sections of normal specimens 

 appearances indicating the phagocytosis of small (presumably 



Text-fig. (3. 



Canipanularia. Zooid cut off at base of hyclrotheca. Dedifferentia- 

 tion to an ellipsoid mass. Many nematocysts were to be seen in 

 the interior. (Camera lucida.) 



Text-fig. 7. 







Diagram showing the manner of occurrence of nematocysts in 

 the interior of the zooid shown in Text-fig. 6. (Observations 

 in vivo.) The nematocysts were loose, or still in their cnidoblast, 

 or ingested in a large endoderm cell, or two inside one endoderm 

 cell. 



interstitial) cells by normal endoderm cells. Professor G. C. 

 Bourne, F.E.S., has kindly informed us that he has seen 

 similar appearances in Hydra, which he also interprets as cases 

 of phagocytosis of one type of cell by another. This process, 

 however, is clearly much commoner in the specimens under- 

 going resorption than in normal zooids. 



It is in any case difficult to see on what occasions phago- 



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