226 ARTHUR DENDY. 



canals as well as beneath the ilermal surface (fig. 43). In all 

 these cases they closely resemble the ordinary stellate meso- 

 derm-cells, and as modifications of such I am for the present 

 disposed to regard them. That they secrete a slime which 

 covers the surface of the sponge in life^ I do not doubt. 



Vesicular Cells. — I propose this name for certain large 

 rounded cells which occur scattered singly, but in considerable 

 numbers, immediately beneath the gastral epithelium of 

 Ute syconoides. The general appearance of these cells is 

 shown in fig. 37. The body of the cell stains uniformly and 

 faii'ly darkly with borax carmine. It is not granular, but 

 hyaline. The nucleus is small, darkly staining, and situated at 

 one side of the cell. It appears to have been pushed aside by 

 the accumulation of fluid in the cell body, as in fat-cells. I 

 am not aware that cells of this kind have been noticed before 

 in calcareous sponges, and they appear to me to be most nearly 

 comparable to the "cystenchyme^^ cells of Silicea and 

 Keratosa — as, for example, Stelospongus (33). 



Reproductive Cells. — The only reproductive cells upon 

 which I have made any observations are the ova, and these 

 have been so frequently described that I need say little about 

 them here. Figs. 34 and 36 represent typical calcisponge ova, 

 consisting each of a large naked body of highly granular 

 protoplasm, with a large, very sharply defined nucleus and a 

 distinct nucleolus. 



In my memoir on Grantia labyrinthica I adduced evi- 

 dence for believing that the ova, at a certain stage of their 

 existence, migrate through the epithelium of the inhalant 

 canals and hang freely from its surface, so as to be bathed by 

 the inflowing stream of water, and I regarded this as a special 

 contrivance for securing fertilisation. In Ute syconoides 

 I have had the good fortune to observe a very beautiful in- 

 stance of the manner in which the ovum hangs suspended from 

 the wall of an inhalant canal, as represented in fig. 35. I was 

 particularly glad to obtain this confirmation of my previous 

 observations, as the inhalant canals of Ute syconoides are 

 much more sharply defined and easily recognisable than those 



