1900.] CuNNlNGTON. — Sea-shore Crabs. 123 



Even further than this may the discriminating powers of 

 these crabs be displayed, for not only will they cover themselves 

 with these protective clothes, but they v/ill take them off 

 again if need be. If a Hyas, covered it may be, by bright- 

 coloured sea-weeds, be placed in a tank, containing, for 

 example, more sombre-coloured sponges, the creature will be 

 found after a little while to have diligently plucked off all the 

 bright colours, and covered itself once more with fragments 

 of the surrounding sponge. There is yet another curious 

 feature about Hyas, in which it differs from other spider-crabs. 

 The pincers are ver}^ white and clean, and the creature is 

 seen to keep them constantly moving, in a rhythmic fashion, 

 these white points thus appearing very conspicuous objects, 

 where the animal is almost hidden by its living covering. The 

 meaning of this apparent anomaly was discovered a few years 

 ago by the Messrs. Dixon, formerly of Trinity College, Dublin. 

 On one occasion they happened to introduce into the tank 

 containing a Hyas a number of small gobies. These little 

 fish had their curiosity at once aroused by this white vibrating 

 structure ; but the moment these investigations brought one 

 well within reach of the concealed crab the unfortunate fish 

 was seized and devoured. Thus, you see, the conspicuous 

 whiteness of the claws really acts as a very efficient lure into 

 the neighbourhood of the watchful, but almost invisible crab. 



Besides Hyas there are several other spider-crabs among 

 the inhabitants of our shore, and the}^ all exhibit more or less 

 this remarkable habit of dressing themselves with the 

 surrounding organisms. Among them I may mention the 

 forms Pisa, Inac/ms, and Macropodia, the I^ong-legged Spider- 

 crab, while Mais sqjiinado, the Spiny Spider-crab, is far the 

 largest of them all. The latter is indeed the largest of all the 

 British species with the exception of the Edible Crab {Cancer 

 pagtcrtis) w^hich, as you know, is sometimes taken of a great 

 size. In some parts it is said to be commonly found as much 

 as nine or ten inches in length. A curious case of companion- 

 ship is sometimes to be made out here, for another little 

 Crustacean, Is^a by name, has been found clinging to the 

 crab's shell, by means of the broad serrated ends of its feet, 

 which are thus specially w^ell adapted for the purpose. Strange 

 to say, this particular form seems to be never found anywhere 

 else. 



