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Show 334: SEXUAL SELECTION. PART II. " was a bloodless one, for I saw no wounds." This same naturalist separated a male sand-ski~per (Ro co~mon on our sea-shores), Gammarus marwus, from Its female both of which were imprisoned in the same vessel ~ith many individuals of the same species. The female beincr thus divorced joined her comrades. After an interva{ the male was again put into the same vessel and be then, after swimming about ~or a time, dashed into the crowd, and without any fi.ghtmg at once took away his wife. 'fbis fact shews that in the Amphipoda, 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 (Birgos latro), found on coral islands, .which makes a~ the bottom of a deep burrow a thwk bed of the pwked 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 performed as well by a young as by an old animal. The following case, however, can hardly be so considered: a trustworthy naturalist, Mr. Gardner/ 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. CHAP. IX. CRUSTACEANS. 335 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. With respect to colour which so often differs in the two sexes of animals belonging to the higher classes, Mr. Spence Bate does not know of any well-marked instances with our British crustaceans. In some cases, however, the male and female 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. In a curious Bornean crab which inhabits sponges, 1\Ir. Bate could always disting~ish the sexes by the male not having the epidermis so much rubbed off. Dr. Power tried to distinguish by colour the sexes of the species which inhabit the Mauritius, but always failed, except with one species of Squilla, probably the S. stylifera, the male of which is described as being "of a beautiful blueish-green," with some of the appendages cherry-red, whilst the female is clouded with l;>rown and grey, " with the red about her much " less vivid than in the male." 10 In this case, we may suspect the agency of sexual selection. With Saphirina (an oceanic genus of Entomostraca and therefore low in the scale) the males are fur~ished with 10 Mr. Oh. Fraser, in 'Proc. Zoolog. Soc.' 1869, p. 3. I am indebted to Mr. Bate for the statement from Dr. Power, |