SEA-FISITERTES LABORATORY. 463 



walking on the bottom. The last pereiopod in Carcinus 

 maenas and Cancer irroratus lias a tuft of setae on the 

 dactylos. According 1 to Smith, the megalopa stage is 

 very short, and at the first moult it changes into a young 

 adult. 



Post-larval stages. The young adult differs from the 

 megalopa in having the abdomen tucked beneath the 

 thorax. It is no longer a pelagic animal, but lives on the 

 bottom, and uses the last four pairs of pereiopods for the 

 purposes of locomotion. As pointed out by Smith* and 

 Cunningham,! the early post-larval stages differ con- 

 siderably from the larger specimens. The carapace is 

 elongated and the rostral region is well developed. The 

 lobes of the antero-lateral border are sharp. Cunningham 

 pointed out that it is difficult to distinguish the early 

 stages of Cancer from those of Atelecyclus heterodon. At 

 each succeeding moult the transverse axis of the carapace 

 increases more rapidly than the longitudinal axis. 



ECONOMICS AND BIONOMICS.I 



The main features in the life-history of the edible 

 crab may be briefly summarised as follows: — 



Cancel 1 pagurus is found all round the coasts of the 

 British Isles, being especially abundant on the rocky 

 coasts. The size at wmich maturity is attained is variable, 

 but most crabs above five inches in breadth may be said 

 to be mature. There appear to be no records of large 



* Smith. Op. cit. 



f Cunningham, J. T. " On the Early Post-larval Stages of the 

 Common Crab (Cancer pagurus), and on the Affinity of that species 

 with Atelecyclus heterodon" Proc. Zool. Soc, 1898, Part II, p. 204. 



| For further information on these subjects see — 



Cunningham. Cornwall County Council : Report of the Executive 

 Committee for Fisheries, 1897-8. Penzance, 189S. 



Williamson. Fishery Board for Scotland : 18tli, 22nd, and "23rd 

 Annual Reports. 



Wilson, Northumberland Sea Fisheries Committee: Reports on 



