VIÏEOLLULA FEllTILIS. 51 



cells in tlie mother sponge, tlie cytoplusui is deeply staiucd and 

 thus makes indistinct the outline of the nucleus, which, except- 

 ing the few chromatic granules contained in it, does not surpass 

 Init rather falls behind the cytoplasm in staining capacity. Fur- 

 ther like them, the larval cells in question either adhere to the 

 reticulum (the trabeculœ) or lie heaped together in the meshes 

 (the trabecular spaces). They are by no means uniformly packed 

 ill, but are for the most part irregularly and apparently rather 

 loosely arranged, so that there exist between them vacant gaps? 

 evidently parts of the lacunar system traversed Ijy the reticular 

 filaments. The gaps may be of quite an insignificant extent, 

 though at other times they may measure 14 // across. While 

 many of them are irregular in outline, others present a more 

 or less roundish section and then may be bordered, either partly 

 or nearly all arouiul, l)y an epithelium-like row of the cells. Such 

 an appearance gives one the impression that he has before him 

 follicle-like structures ; and at first I even thought of the pos- 

 sibility of their representing the Anlagen of the chambers. How- 

 ever, after more concentrated observations, I have had to throw 

 off this illusion, 1)ecause : firstly, several closely situated follicle- 

 like spaces, though a})parently distinct at first sight, could often 

 be demonstrated to be parts of a continuous lacunar space ; 

 secondly, they are at places found to be partitioned from one 

 another l)y a single row of the cells, which should not be the 

 case if each were a follicle having a wall of its own ; and third- 

 ly, it not infrequently happens that the inner space is distinctly 

 traversed by the filaments of the reticulum. After all, I Ijelieve 

 the cellular mass is simply honeycombed, as it were, by a system of 

 interstitial lacunie, which are the same as the meshes of the reticu- 

 lum. In other words it iiiav be said that the cells are, at least 



