14 



kind of fatty food material Avliicdi we may call yoll\, 

 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 n\icleus to 

 one .-ide of the ovnm (Plate II., tig. l-l). In the males 

 the group of [)rimary sexual cells that aie .formed on the 

 mesenteries in the spring rindergo rapid cell diA-fsion, and 

 a spermary is thus formed, [lacked with very minute cells. 

 The piotoplasm of these cells is so tightly pressed together 

 that the speiniary has the appearance of heing a single 

 cell, with an enormous number of nuclei. When the 

 spermaiy is about O'l mm. in diameter, the cells collect 

 towards the periphery, leaving a rounded space containing 

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

 This central body may coirespond with the " blasto})hore,'' 

 Avhich occurs in the spermatogenesis of some other 

 animals. The ripe s})ermatozoa 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. 



l)EVELorMENT. 



When the ova are ripe, they are aboui ()'5 mm. in 

 diameter, and they are discharged into the water by wav 

 of the mouth the stomodaeum distending considerably to 

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

 be seen in an a(|uarium, the spawning is a very lengtliv 

 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 gieat masses," as they are 

 in Ren ill a, according to Wilson. 



The early stages of development are probably verv 

 variable as regards the external signs of segmentation. 



