334 
SEXUAL SELECTION. 
Paet II- 
“ was a bloodless one, for I saw no wounds.” This 
same naturalist separated a male sand-skipper (so coin' 
mon on our sea-shores), Gammarus marinus, from its 
female, both of which were imprisoned in the satD® 
vessel with many individuals of the same species. Th® 
female being thus divorced joined her comrades. Aft® r 
an interval the male was again put into the sam® 
vessel and he then, after swimming about for a time* 
dashed into the crowd, and without any fighting at one® 
took away his wife. This fact shews that in the Amph J ' 
poda, an order low in the scale, the males and femal eS 
recognise each other, and are mutually attached. 
The mental powers of the Crustacea are probably 
higher than might have been expected. Any one w h° 
has tried to catch one of the shore-crabs, so numero« s 
on many tropical coasts, will have perceived how war?' 
and alert they are. There is a large crab (Bir0 3 
latro), found on coral islands, which makes at th® 
bottom of a deep burrow a thick bed of the pick®® 
fibres of the cocoa-nut. It feeds on the fallen fruit ot " 
this tree by tearing off the husk, fibre by fibre; 
it always begins at that end where the three cy®' 
like depressions are situated. It then breaks through 
one of these eyes by hammering with its heavy fro® 1 
pincers, and turning round, extracts the albumin®’ 15 
core with its narrow posterior pincers. But these actio® 6 
are probably instinctive, so that they would be p® 1 
formed as well by a young as by an old anin® 1 * 
The following case, however, can hardly be so c® 11 
sidered : a trustworthy naturalist, Mr. Gardner, 9 whu s 
watching a shore-crab (Gelasimus) making its burro*’ 
• ‘Travels in the Interior of Brazil,’ 1846, p. 111. I have g-iven,^^ 
my ‘ Journal of Besearches,’ p. 463, an account of the habits of 
Birgos. 
