ON DIGESTION IN THE CCELENTERA. 449 



In the oral region of the stomach the endoderm was of 

 a different character and never contained food particles. 

 In those forms which were, in all probability, in a hungry 

 condition, numerous large clear goblet cells were observed, 

 which were shed apparently in the specimens captured in 

 the act of digestion. 



The conclusion was therefore drawn that, in addition to 

 the ordinary process of intracellular digestion, a secretion 

 may be poured into the cavity of the stomach from the 

 goblet cells, or secretion cells as they were more correctly 

 termed, which probably exerts some digestive action upon 

 the larger forms of prey, outside the cell-layers. 



In other words, in addition to the process of intra- 

 cellular digestion, there is a process of extracellular di- 

 gestion, the latter being perhaps only preparatory to the 

 former. 



A few years later Jickeli and Nussbaum described in 

 the endoderm of Hydra, in addition to the ordinary large 

 vacuolated cells, certain smaller forms which were called 

 gland cells. 



A physiological investigation of these cells led Miss 

 Greenwood, in 1888, to the conclusion that the digestion of 

 the food of Hydra takes place entirely outside the endoderm 

 cells, that the small pyriform bodies found in gland cells are 

 poured into the body cavity during digestive activity in the 

 form of a fluid secretion, and that the products of digestion 

 are taken up by the large vacuolated cells in a fluid form 

 for storage and subsequent distribution. 



These results, then, though differing in some minor 

 points from those obtained by Lankester in Limnocodium, 

 confirmed his conclusion as to the secretion of a fluid into 

 the cavity of the Hydroid by certain cells of the endoderm. 



Further evidence upon this point was obtained by 

 Hardy, who made an elaborate investigation of the endo- 

 derm of Myriothela phrygia. He found that the food of 

 this Hydroid, which consists chiefly of small Crustacea, is 

 digested at first in the lower portion of the tentacle bearing 

 region where the gland cells are most abundant, and is due 

 to a digestive fluid poured into the cavity and secreted by 



