468 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY, 



doubt that many crabs do not bear their first batch of eggs 

 until attaining a size of six inches. 



Male.— The male crabs evidently attain maturity at 

 a smaller size than is the case in the females. Probably 

 all males above four and a half inches are mature, and 

 Williamson has found mature males below this size. 



Fertilisation takes place in the inshore waters during 

 the late summer and autumn, and is effected immediately 

 after the female has cast. The one supply of spermatozoa 

 is probably sufficient for two successive batches of eggs, 

 and even three in the older crabs. The spermatozoa 

 remain in the spermathecae, and the entrances to the 

 latter are closed by plugs, which are probably formed by 

 a secretion from the walls of the spermathecae which 

 hardens in contact with water. 



The spawning of the eggs is effected in the deeper off- 

 shore waters during the winter. The eggs are attached 

 to the endopoditic setae of the pleopods, and remain there 

 until the following summer, wmen they are hatched in the 

 inshore waters. 



The crab probably does not cast after the larvae are 

 hatched, but a second batch of eggs are spawned in the 

 following winter in the offshore waters. As with the 

 first batch, the developing embryos will be retained on the 

 abdominal appendages until the following summer, when 

 the hatching process will again take place in the inshore 

 waters. After the second hatching the female probably 

 casts, and is fertilised. 



The developing embryos probably remain attached to 

 the pleopods for about seven months. The various zoea 

 stages and the megalopa stage may extend over a period of 

 two months, but our knowledge of the larval stages of 

 Cancer is remarkably scanty. It is probable that the 

 larvae hatched at the end of June will be in the first 

 adult stage about the end of August. 



