CRUSTACEANS. 265 



seize and to secure the female, and this in some instances, as 

 with Gammarus, is Icnown to be the case. The male of the her- 

 mit or soldier crab (Pagurus) for weeks together, carries about 

 the shell inhabited by the female." The sexes, however, of the 

 common shore-crab (Caroinus msnas), as Mr. Bate informs me, 

 unite directly after the female has moulted her hard shell, when 

 she Is so soft that she would be injured if seized by the strong 

 pincers of the male; but as she is caught and carried about by 

 the male before moulting, she could then be seized with impunity. 



Fritz Miiller states that certain species of Melita are distin- 

 guished from all other amphipods by the females having "the 

 "coxal lamellas of the penultimate pair of feet produced into 

 "hook-like processes, of which the males lay hold with the hands 

 "of the first pair." The development of these hook-like proc- 

 esses has probably followed from those females which were the 

 most securely held during the act of reproduction, having left 

 the largest number of offspring. Another Brazilian amphipod 

 (Orchestia Darwinii, flg. 8) presents a case of dimorphism, like 

 that of Tanais; for there are two male forms, which differ in the 

 structure of their chelae." As either chela would certainly suf- 

 fice to hold the female, — for both are now used for this purpose, 

 — the two male forms probably originated by some having va- 

 ried in one manner and some in another; both forms having 

 derived certain special, but nearly equal advShtages, from their 

 differently shaped organs. 



It is not known that male crustaceans fight together for the 

 possession of the females, but it is probably the case, for with 

 most animals when the male is larger than the female, he seems 

 to owe his greater size to his ancestors having fought with other 

 males during many generations. In most of the orders, espe- 

 cially in the highest or the Brachyura, the male is larger than the 

 female; the parasitic genera, however, in which the sexes follow 

 different habits of life, and most of the Entomostraca must be 

 excepted. The chelae of many crustaceans are weapons well 

 adapted for fighting. Thus when a Devil-crab (Portunus puber) 

 was seen by a son of Mr. Bate fighting with a Carcinus masnas, 

 the latter was soon thrown on its back, and had every limb torn 

 from its body. When several males of a Brazilian Gelasimus, a 

 species furnished with immense pincers, were placed together in 

 a glass vessel by Fritz Miiller, they mutilated and killed one 

 another. Mr. Bate put a large male Carcinus msenas into a pan 

 of water, inhabited by a female which was paired with a smaller 

 male; but the latter was soon dispossessed. Mr. Bate adds, "if 



" Mr. C. Spence Bate, 'Brit. Assoc, Fourth Report on the Fauna of 

 3. Devon.' 

 13 Fritz Muller, 'Facts and Arg^uments for Darwin," 1869, pp. 25-28. 



