CRUSTACEANS. 267 



The mental powers of the Crustacea are probably higher than 

 at first sight appears probable. Any one who tries to catch one 

 of the shore-crabs, so common on tropical coasts, will perceive 

 how wary and alert they are. There is a large crab (Blrgus 

 latro), found on coral islands, which makes a thick bed of the 

 picked fibres of the cocoa-nut, at the bottom of a deep burrow. 

 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 turn- 

 ing round, extracts the albuminous core with its narrow posterior 

 pincers. But these actions are probably instinctive, so that 

 they would be performed as well by a young animal as by an old 

 one. The following case, however, can hardly be so considered: 

 a trustworthy naturalist, Mr. Gardner," whilst watching a shore- 

 crab (Gelasimus) making its burrow, threw some shells towards 

 the hole. One rolled in, and three other shells remained within 

 a few inches of the mouth. In about five minutes the crab 

 brought out the shell which had fallen in, and carried it away to 

 the distance of a foot; it then saw the three other shells lying 

 near, and evidently thinking that they might likewise roll in, 

 carried them to the spot where it had laid the first. It would, I 

 think, be difficult to distinguish this act from one performed by 

 man by the aid of reason. 



Mr. Bate does not know of any well-marked case of difference 

 of color in the two sexes of our British crustaceans, in which 

 respect the sexes of the higher animals so often differ. In some 

 cases, however, the males and females differ slightly in tint, but 

 Mr. Bate thinks not more than may be accounted for by their 

 different habits of life, such as by the male wandering more 

 about, and being thus more exposed to the light. Dr. Power 

 tried to distinguish by color the sexes of the several species which 

 Inhabit the Mauritius, but failed, except with one species of 

 Squilla, probably S. stylifera, the male of which is described as 

 being "of a beautiful bluish-green," with some of the appen- 

 dages cherry-red, whilst the female is clouded with brown and 

 gray, "with the red about her much less vivid than in the male."" 

 In this case, we may suspect the agency of sexual selection. 

 From M. Bert's observations on Daphnia, when placed in a vessel 

 illuminated by a prism, we have reason to believe that even the 

 lowest crustaceans can distinguish colors. With Saphirina (an 

 oceanic genus of Entomostraca) , the males are furnished with 



" '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 

 Birgus. 



15 Mr. Ch. Fraser, in 'Proc. Zoolog.. Soc.,' 1869, p. 3. I am indebted 

 to Mr. Bate for Dr. Power's statement. 



