334 SEXUAL SELECTION. Part II. 



" was a bloodless one, for I saw no wounds." This 

 same naturalist separated a male sand-skipper (so com- 

 mon on our sea- shores), Gammarus marinus, from its 

 female, both of which were imprisoned in the same 

 vessel with many individuals of the same species. The 

 female being thus divorced joined her comrades. After 

 an interval the male was again put into the same 

 vessel and he then, after swimming about for a time, 

 dashed into the crowd, and without anv fight-ins: at once 

 took away his wife. This fact shews that in the Amphi- 

 poda, an order low in the scale, the males and females 

 recognise each other, and are mutually attached. 



The mental powers of the Crustacea are probably 

 higher than might have been expected. Any one who 

 has tried to catch one of the shore-crabs, so numerous 

 on many tropical coasts, will have perceived how wary 

 and alert they are. There is a large crab (Birgus 

 latro), found on coral islands, which makes at the 

 bottom of a deep burrow a thick bed of the picked 

 fibres of the cocoa-nut. It feeds on the fallen fruit of 

 this tree by tearing off the husk, fibre by fibre ; and 

 it always begins at that end where the three eye- 

 like depressions are situated. It then breaks through 

 one of these eyes by hammering with its heavy front 

 pincers, and turning round, extracts the albuminous 

 core with its narrow posterior pincers. But these actions 

 are probably instinctive, so that they would be per- 

 formed as well by a young as by an old animal. 

 The following case, however, can hardly be so con- 

 sidered : a trustworthy naturalist, Mr. Gardner, 9 whilst 

 watching a shore-crab (Gelasimus) making its burrow, 



9 'Travels in the Interior of Brazil,' 1846, p. 111. I have given, in 

 my ' Journal of Researches,' p. 463, an account of the habits of the 



Birgos. 



