BRITISH STALK-EYED CRUSTACEA. 13 



The colour of this common hut interesting species varies 

 more than that of any other of the British Crustacea, and it is no 

 doubt from the protection that is derived from its very close 

 resemblance in this respect to its surroundings that it is of such 

 wide distribution. On the sandy beaches of most of our shores 

 this crab is invariably of a yellowish or reddish brown colour, the 

 latter tint being more prominent in localities where the sand 

 partakes of a ferruginous character. In estuaries or on shores of 

 a clay or mud deposit, such as at the mouth of the Medway, the 

 colour again becomes assimilated to the surroundings, the animal 

 being of a dull brown, frequently tinged with green. In the 

 rock-pools, however, of such highly favoured localities as the 

 Channel Islands, where, in hollows in the syenitic or dioritic 

 rocks, the Zostera, Ulva, and other richly tinted Algae are in 

 almost tropical profusion, there it is that the most beautiful 

 colours of Carcinus meenas are developed. Instead of the sombre 

 shades of the inhabitants of sandy or muddy shores we have here 

 specimens marked with the brightest green mottled with white. 

 So striking is the resemblance to its surroundings in these 

 localities that it is at times almost impossible to detect the animal 

 unless it moves. 



Even in the tanks of the Westminster Aquarium, this adapta- 

 tion of colour, as a means of protection, can be clearly observed. 

 Specimens from different localities and of different shades have 

 become of one hue after a short existence under such new 

 conditions of life, those inhabiting tanks with a sandy bottom 

 becoming unicolorous, whilst those in tanks with a shingly floor 

 assume a mottled appearance. 



The geographical distribution of Carcinus meenas is remark- 

 able ; not only is it extremely abundant on almost all parts of the 

 coasts of the British Islands, but according to the 'Annals and 

 Magazine of Natural History' (1874, vol. xiii. p. 405), quoting the 

 ' Proceedings of the Asiatic Society of Bengal' (November, 1873), 

 Dr. J. Anderson is stated to have taken it at Point de Galle. 

 Besides this it has been recorded from the coasts of North 

 and South America, as well as from the Arctic Ocean and the 

 Mediterranean. 



Carcinus meenas is of much service as well as of considerable 

 annoyance to fishermen. It is crushed and used by them as bait 

 for the whelk-pots. At Shoreham the children are often employed 



