BY R. VON LENDENFELD, PH.D. 905 



The cilated chambers ai-e simple sac-shaped, and in their 

 proximal part cylindrical, and not contracted towards the cir- 

 cular opening into the Gastral cavity 



The most interesting part of our animal is tlie Entoderm : It 

 consists, as mentioned above, throughout of the same flagellate 

 cells. This can be seen in the living Sponge, but still better in 

 Osmic-acid specimens. The peculiar short cylindrical shape which 

 the flagellate cells attain, when hardened, the large, highly 

 colourable nucleus, and the regular network of boundary-lines 

 between the cells is the same throughout the inner surface of the 

 Sponge. 



The cells correspond to the well-known shape of the flagellate, 

 frilled Sponge cells. 



It is particularly remarkable that the same cells also cover the 

 inner surface of the Spongorhiza. 



We find in our Sponge an Entoderm, which is not difi"erentiated 

 into difi'erent kinds of cells, whilst a higher development in the 

 direction of the Syconidse has already been attained by the Sponge, 

 in consequence of the folding ])rocess which has produced the 

 ciliated chambers. This would appear altogether exceptional. 

 Generally the cells are diflerenciated first, and then Organs of a 

 whole complex of such difierentiated elements are formed. 



The exception is, however, I think, not actual, but only 

 ap]iarent. I am inclined to believe that the Mesoderm is, in our 

 case, the active part growing, more or less, in different parts, and 

 so forcing the Entodermal layer to attain a complicated structure, 

 which is not caused by the cells of the latter. 



The Ectoderm consists of the ordinary flat cells, and is the 

 same throughout. 



The Mesoderm also presents no peculiar character. 

 The Skeleton consists of seven different kinds of spicules. 1- 

 Gastric quadriradiates ; 2. Parenchymal Quadriradiates ; 3. Par- 

 enchymal triradiates ; 4. Dermal triradiates ; 5. Dermal acerates 

 thick ; 6. Dei-mal acerates slender ; and 7, Oscular acerate spicules. 

 1. The gastric quadriradiate spicules are found all over the 

 inner surface. Three tangental rays lie in one plane in the 



