84 A HISTORY OF EECENT CRUSTACEA 



Since it is during this period of ' mouldering ' that the 

 crabs are fattest and best flavoured, Herbst finds it easy 

 to suppose that greedy man will not leave them safe in 

 their repose. On the contrary, he busily digs them out 

 with a spade. Considering how readily under some cir- 

 cumstances these crustaceans shed their limbs, it is singu- 

 lar that in exuviation they are able to cast off their whole 

 caparison so uninjured and complete that it might be mis- 

 taken for the living animal. Careful inspection is required 

 to perceive near the insertions of the limbs the ventral slit 

 through which the animal has made its escape. 



It was in a West Indian species of Gecarcinus that 

 Professor Westwood observed that the young issued from 

 the egg in a form not materially different from that of 

 their parents. This experience, combined with Rathke's 

 similar observation in regard to the European crayfish, 

 led him at first to throw doubt upon Vaughan Thompson's 

 theory of crustacean metamorphoses. But it was soon 

 brought to light that the examples of the land-crab and 

 the freshwater crayfish were interesting exceptions to a 

 still more interesting rule, and there are few who would 

 now deny that these exceptions are to be explained as 

 modifications in the life-history of the animals concerned, 



i7 



acquired late in the course of time to suit the new condi- 

 tions of existence encountered by creatures emerging from 

 the sea to a life in fresh water or on dry ground. That no 

 crustaceans have been able to cut themselves loose from 

 some dependence upon moisture is not very wonderful, 

 since in that respect man himself is still an aquatic 

 animal. 



Gecarcinus lagostoma, Milne-Edwards, represented on 

 Plate II, is a widely distributed species. 



Hi/lceocarcinus Humei, Wood-Mason, occurs in ' the 

 dark dense damp forests of the Nicobar Islands.' 



Uca una (Linn.), the crab of the mangrove swamps of 

 Brazil, may be mentioned as a rare instance of one that 

 has been allowed to possess the names by which it was 

 figured and described centuries ago. In this genus the 

 last joints of the walking legs are compressed and un- 



