A SUBAQUEOUS CITY. 153 



The former undergo a process of granulation, and 

 become filled with small flagellate rod -like sperma- 

 tozoa, which eventually escape, and coming into 

 contact with, are absorbed by, the now mature 

 nucleated germ cells. These are thus impregnated, 

 and in this condition of a fecundated egg, pass 

 through the usual process of segmentation, the 

 contents assuming the morula or mulberry -like state, 

 followed by the external development of cilia, when 

 the egg-form embryo by its means is enabled to 

 swim about as an independent organism in the 

 surrounding water. There is no hatching process 

 of this egg. It is itself the young Sponge in 

 embryo, working out its destiny to the mature 

 Sponge city before described. 



This sexual development does not seem to be 

 necessary except as a sort of more vigorous renewal 

 or reproduction, and is in consequence only occa- 

 sionally resorted to. The more common method 

 being the production of non-sexual egg-like forma- 

 tions of the Sponge tissue, which are at once set 

 free in great numbers as ciliated embryos, through 

 the osculum, and then go through the usual subse- 

 quent stages to perfect Sponges, 



