ON DIGESTION IN THE C03LENTERA. 451 



supplementary one, or are the functions referred to not 

 confined to any one region or set of organs in the Anthozoan 

 anatomy?" 



Concerning the function of the stomodaeum we have 

 very little experimental evidence. 



The Hertwigs and others have shown that the epi- 

 thelium lining the inner walls does contain among the 

 columnar ciliated cells of which it is mainly composed a 

 certain number of gland cells which are histologically of 

 two kinds, but to what extent these cells assist in the 

 digestion of the food has not been experimentally deter- 

 mined. 



In the Alcyonaria no gland cells are found in this 

 region, and it seems probable that the stomodaeum in all 

 Anthozoa is simply a food passage, and plays, at most, a very 

 small part in the process of digestion. In all Anthozoa, 

 however, the epithelium of the mesenterial filaments — with 

 the exception of the two dorsal ones in Alcyonaria — is 

 crowded with gland cells, and there can be no doubt that 

 they secrete a fluid which disintegrates and dissolves the 

 food. 



When the food has passed through the stomodaeum, it 

 may be seen in certain transparent polyps to be seized by 

 the filaments and held in their grasp until it is disintegrated 

 and partly dissolved. Krukenberg described the filaments 

 of sea-anemones as being wound about the food, and Wil- 

 son found that in Leptogorgia virgulata — an Alcyonarian — 

 the food was " held closely clasped by the mesenterial 

 filaments for two or three hours," and that afterwards "a 

 mass of refuse matter was passed out through the oesopha- 

 gus," i.e., stomodaeum, "and the filaments resumed their 

 normal position ". 



There can be little doubt, then, that these organs do 

 secrete a digestive fluid in the Alcyonaria, and there can 

 be little doubt that the gland cells which secrete this fluid 

 are chiefly confined to these filaments. But is the absorp- 

 tion of the food either in a fluid state or in a particulate 

 form confined to the cells of the filaments, or to the cells of the 

 general endoderm lining of the body cavity, or does it occur 



