SEAT-FISHERIES LA BORATOR V . 473 



Condition of ovary. During the spring 

 and summer the ovary remains unusually small, and has 

 a pale colour. The eggs are mostly small and without 

 yolk. 



Fourth Year. September — The crab casts and is fertilised. 



During these processes the crab is in the inshore 

 waters. Immediately after fertilisation the offshore 

 migration will commence, and the whole of the above 

 history will be repeated. • 



Condition of ovary. Similar to that at the 

 first casting. 



Bionomics of Ecdysis. 



As already seen, the growth of the crab can only take 

 place by the exuviation of hard shell or exoskeleton. 

 Immediately after ecdysis has taken place the body — now 

 covered by a soft flexible membrane — increases consider- 

 ably in size. In the mature female fertilisation is also 

 effected while the crab is soft. The soft crabs are not fit 

 for food, and it is illegal to expose them for sale when in 

 this condition. 



Season of casting. 



The young crabs cast at various times of the year, but 

 after the third year ecdysis generally takes place in the 

 autumn. According to Williamson, the main casting 

 period on the East Coast of Scotland is from July to 

 September, but it may be extended to December. From 

 August to November appears to be the chief casting time 

 in the Isle of Man. The casting is effected in the warmer 

 inshore waters. The hardening process in the mature 

 crab lasts from three to five months, according to 

 Williamson. 



