SEX AND BREEDING 



53 



Fig. 8. Young sea urchins in brood pouch of the Falkland Islands sea urchin, 



Goniocidaris canaliculata. After Sir C. Wyville Thomson in The Voyage of the 



''Challenger" The Atlantic. Vol. II, p. 224, 1877. 



Arbacia is different from the starfish, Asterias forbesi, which sheds its 

 eggs in the germinal vesicle stage, and maturation of the eggs takes 

 place after they are laid. These (starfish) eggs should be fertilized 

 during or just after the first maturation division, one to one and a half 

 hours after removal from the animal. 



When Arbacia are brought in from the sea after the middle of August, 

 many of them have already shed. By September first, most of the ani- 

 mals have shed, although one finds a few with eggs and many with 

 sperm. If, however, the animals are brought into the laboratory earlier 

 in the season before they have shed, and kept in aquaria (capacity 16 

 gallons or more) with running sea water, they retain their eggs and 

 sperm and remain in good condition through October (E. B. Harvey, 

 1939b). The animals require no special food, but apparently they eat 



