416 Miscellaneous. 



the rest of the animal being of a dingy greenish-brown colour, I have 

 been able to observe that, whatever other functions the great chela may 

 serve — whether as a stopper to the mouth of the burrow, or as a 

 nuptial support, as some have supposed — it also, in the species under 

 consideration, is (i) a club used in the contests of rival males, and 

 (ii) a signal to charm and allure the females. This last function is 

 particularly apparent. As one walks across the mud one first 

 becomes aware of the presence of these crabs by noticing that the 

 surface of the mud is everywhere alive with twinkling objects of a 

 brilliant pearly pink colour. Carefully watched, these prove to be 

 the enormous chelae of a crowd of males of Oelasimus, waving in the 

 air, each little crab standing at the mouth of its burrow and cease- 

 lessly brandishing its big claw. On closer observation, among every 

 ten or so males a small clawless female may be seen feeding in 

 apparent unconcern. If the female should approach the burrow of 

 a male, the latter displays the greatest excitement, raising itself on 

 its hindmost legs, dancing and stamping, and frantically waving its 

 beautifully coloured big claw. From prolonged watching I feel 

 convinced that the waving of the claw by the male is a signal of 

 entreaty to the female, and I think that no one can doubt that the 

 claw of the male has become conspicuous and beautiful in order to 

 attract and charm the female. 



The second function, as a fighting weapon, becomes apparent 

 when in the general tournament one of the rival males approaches 

 too close to another. 



The great claw is then used as a club, the little creatures making 

 savage back-handed sweeps at each other. When two males were 

 put into a bucket together the larger immediately gave chase to the 

 smaller, and with one blow swept him off his feet. I did not 

 actually see the rival males seize each other in the conflict, but I 

 have no doubt that they do so, for on going over the field of action 

 I saw several freshly dismembered chelie lying on the mud. So 

 that the chela is probably used as a shears as well as a club. 



It seems likely that the claw primarily became enlarged as a 

 fighting weapon : but this, though it explains its size and weight, is 

 not suificient to account for its wonderfully conspicuous beauty, 

 which, of itself, must make the little animal, otherwise sombrely 

 coloured in harmony with its habitat, a mark to its enemies. 



We can only suppose that the colour and brilliance has been 

 secondarily acquired in order to attract and please the female. — 

 From the Administration Rejiort of the Marine Survey of India for 

 1891-92. 



