268 THE DEEP-SEA CRUSTACEA 



the males of some species for catching their partners, 

 and in Parape^ieus rectacuhis (Fig. 62) we see how 

 they are turned into a sort of crook for this purpose. 

 This has long been thought to be their function in the 

 prawns of the oceanic genus Sergestes, In the males 

 of certain other deep-sea prawns the third pair of foot- 

 jaws are modified in a way which can only mean that 

 they are used for hooking on to a partner of the 

 opposite sex : foot-jaws of this strange kind are best 

 seen in Aristmis crassipes (Fig. 63). 



In those deep-sea forms whose nippers are greatly 

 enlarged, these of course will be used, as they are by 

 many shore-crabs, for the subjugation of rivals, and 

 for the compulsion of the female. In no case is this 

 better illustrated than it is by the deep-sea hermit- 

 lobsters of the genus Munida, in many species of 

 which the great chelipeds — one or both — of the adult 

 male are more curiously and vastly more strongly 

 fashioned than those of the female and young 

 unseasoned male. 



There are some deep-sea prawns of the genus 

 AristcBus in which the antennal scale of the male alone 

 is curiously lengthened and thickened, but for what 

 particular purpose we cannot say, though Spence Bate 

 considered that it is a prehensile apparatus. Aristceus 

 edwardsiamts, Johnson, an Atlantic species which is 

 also common in Indian waters, furnishes the best 

 example of this. 



