450 SCIENCE PROGRESS. 



those gland cells. The result of this digestion is the dis- 

 integration of the food into a number of fragments which 

 float freely in the fluid of the cavity, and the solution of a 

 considerable quantity of the proteids of the prey which may 

 be precipitated by treatment with corrosive sublimate. It 

 was further shown that many of the fragments are taken 

 up by the endoderm cells and digested within the cell 

 substance, whilst the vacuolated cells of the endoderm be- 

 come loaded with granules — the so-called nutritive spheres 

 — which are formed from the products of digestion in 

 solution in the ccelenteric cavity. 



The general results of these investigations have proved 

 then that in the Hydroids two kinds of endoderm cells 

 occur, namely, secreting gland cells and vacuolated cells 

 for the absorption and storage of the product of digestion 

 in the fluid form, and that in some Hydroids, but not ap- 

 parently in Hydra, the intracellular digestion of a portion 

 of the food may occur. 



In the Hydrozoa the cavity of the body is simple and 

 continuous, and although different regions may be defined 

 in which the two or more varieties of endoderm cells may 

 be predominant, no special digestive organs of definite 

 shape can be recognised upon simple dissection and ex- 

 amination with a lens. 



In the Anthozoa, however, a more complicated struc- 

 ture is observed. The mouth opens into a short tube, 

 which is ectodermic in origin, called the stomodseum, and 

 this is connected to the body wall by a number of partitions 

 or mesenteries lined on both their surfaces by endoderm 

 cells. Their free edges are somewhat convoluted, are 

 provided with a thickened epithelium, and are termed the 

 mesenterial filaments. 



The question then naturally occurs : " Have we in this 

 more complicated structure some separation of the cells 

 which in the Hydrozoa perform the functions of digestion?" 

 Or to put the same question in other words : " Does the 

 epithelium of the mesenterial filaments perform the function 

 of secretion or absorption only, and the remainder of the 

 endoderm lining the body walls and mesenteries the 



