BRITISH STALK-EYED CRUSTACEA. 103 
part of their time, combined perhaps with some change in 
the kind of food within reach. This question of colour- 
variation is of some interest, for the boring species of the 
genera Axius, Gebia, Callianassa, &c., are all of a pale hue, 
generally in fact of a most unhealthy-looking paleness, owing 
to the absence of light which these species generally experience 
during the greater part of their lives. With regard to Mollusca 
this feature is often very striking. When visiting the large caves 
in Sark, some years ago, I found some intensely white varieties 
of the common Dog Whelk, Purpura lapillus, in a very dark and 
sheltered cave, the floor of which was a rock-pool at low tide: 
whilst outside on the exposed and sun-lit shore the same species 
was to be found of red, yellow, brown, and blackish tints. I 
merely mention this to support what I say with regard to the 
question of habitat in respect to light, which I think is more 
likely to cause variation than geological or climatic conditions. 
Many crustaceans adapt themselves to the pervading tint of 
surrounding objects, as, for instance, the common Shore Crab, . 
Carcinus menas, which is a dull brown in muddy harbours, 
yellow when living on a sandy shore, and beautifully mottled 
with green and white when inhabiting shelly rock-pools amongst 
Ulva and Zostera; many others also, being dwellers on sandy 
bottoms, are yellowish brown, as, for example, the genera Hyas, 
Inachus, &c.; or red and brown, as those which live among 
granite boulders, such as Xantho and Maia. The lobster, 
however, does not appear to enjoy such protection, possibly 
because able to hold its own by other means. It is quite 
possible when hauling lobster-pots to look over the side of the 
boat, if in clear still water, and see the lobsters distinctly when 
other crustaceans and fish are invisible, except when any 
movement on their part betrays their whereabouts. 
The question of lobsters “‘shooting” their claws is an 
interesting one, inasmuch as such a performance is unwelcome 
to the fisherman, spoiling as it does the market value of the 
Lobster. All crustaceans, or at any rate all the stalk-eyed 
forms, appear to part readily with limbs under influence of fear 
or desire to escape, and to be able also to reproduce them during 
future exuviation and growth; some appear to be much more 
addicted to this peculiarity than others, for I once captured a 
specimen of Xantho rivulosa which cast the whole of its ten legs 
