ALCYONIUM. 105 



kind of fatty food material which we may call yolk, 

 appear in its cell substance. The only other changes that 

 take place during the last six months of the year are the 

 appearance of a yellowish red pigment at the periphery 

 and, in the last month, the transit of the large nucleus to 

 one side of the ovum (Plate II., fig. 13). In the males 

 the group of primary sexual cells that are formed on the 

 mesenteries in the spring undergo rapid cell division, and 

 a spermary is thus formed, packed with very minute cells. 

 The protoplasm of these cells is so tightly pressed together 

 that the spermary has the appearance of being a single 

 cell, with an enormous number of nuclei. When the 

 spermary is about 0*1 mm. in diameter, the cells collect 

 towards the periphery, leaving a rounded space containing 

 strands and lumps of protoplasm (Plate II., fig. 14). 

 This central body may correspond with the " blastophore," 

 which occurs in the spermatogenesis of some other 

 animals. The ripe spermatozoa which are only found in 

 December completely fill the cavity of the spermary. They 

 consist of a head with a cone-shaped anterior end, followed 

 by a spherical body, and a long flexible tail. 



Development. 



When the ova are ripe, the} T are about 0'5 mm. in 

 diameter, and they are discharged into the water by way 

 of the mouth the stomodaeum distending considerably to 

 allow them to pass. If we may judge from what ma}' 

 be seen in an aquarium, the spawning is a very lengthy 

 process, as each ovum takes at least ten minutes to pass 

 through the stomodaeum. At any rate, they do not 

 appear to be " vomited forth in great masses," as they are 

 in Renilla, according to Wilson. 



The early stages of development are probably very 

 variable as regards the external signs of segmentation. 



