458 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



whole of the dorsal side of the cephalothorax. They are 



of an orange-red colour, and the separate eggs can he 

 readity distinguished. The red colour is due to the 

 presence of the food-yolk. The yolk granules form the 

 main part of the mature ovum (fig. 79). With regard to 

 the condition of the ovaries between two processes of 

 ecdysis, the reader is referred to the section on Bionomics. 



Copulation takes place immediately after the female 

 has cast, and while it is still in a soft condition. 

 Apparently the spermatozoa burst free from the spermato- 

 phores as soon as they leave the vas deferens. In the 

 spermatheca only free , spermatozoa are found. After 

 copulation the cells lining the spermatheca secrete a fluid 

 which fills the cavity of the oviduct. This secretion 

 hardens upon contact with the sea water, and thus the 

 oviducts become effectively plugged, and the contents of 

 the spermatheca cannot escape. It is a remarkable fact 

 that the spermatozoa remain inside the spermatheca for 

 many months before they fertilise the ova. 



The eggs are spawned in the winter. Upon reaching 

 the exterior, each egg is probably surrounded by two 

 membranes — an inner vitelline membrane and an outer 

 chorion. Between the two is a perivitelline space, which, 

 according to Williamson, contains a fluid possessing 

 adhesive properties. The eggs become attached to the 

 endopodite setae of the abdominal appendages. The 

 interesting question regarding the mode of attachment of 

 the eggs to the endopodite setae is not yet conclusively 

 settled. Some of the early observers believed that a 

 stick}^ substance was secreted around the eggs as they 

 were being shed. This, however, would not explain why 

 the eggs become attached only to the endopodite setae. 

 Herrick's* explanation is that the tegumentary glands of 

 * Herrick. " The American Lobster," Bull. U.S. Fish Com., 1895. 



