78 THE COLOUES OF ANIMALS 



and the spiral line of fragments extends for a certaia 

 distance, and is then suddenly replaced by spines 

 which are doubtless of value as a defence. In X. cerea 

 and X. solaroides the size of the adventitious particles 

 is so great as to nearly conceal the shell, while in 

 X. conchyliophora nothing can be seen but a heap of 

 fragments. Specimens of Xenophora and of the crabs 

 mentioned below are to be seen in the Museum of 

 the Eoyal College of Surgeons, as part of a beautiful 

 series intended by Professor Stewart to illustrate the 

 various uses of the colours of animals. 



The tube of certain well-known marine worms 

 {Terehellidce) is constructed of sand-grains cemented 

 together. 



One of the most interesting examples of adventi- 

 tious protection is afforded by certain crabs {Steno- 

 rhynchus, Inachus, Pisa, Main), which fasten pieces of 

 sea- weed, &c., on their bodies and limbs. Bateson 

 has watched the process in Stenorhynehus and Inachus, 

 ' The crab takes a piece of weed in his two chelae, and, 

 neither snatching nor biting it, deliberately tears it 

 across, as a man tears paper with his hands. He 

 then puts one end of it into his mouth, and, after 

 chewing it up, presumably to soften it, takes it out 

 in the chelae and rubs it firmly on his head or legs 

 until it is caught by the peculiar curved hairs which 

 cover th m. If the piece of weed is not caught by 

 the hairs, the crab puts it back in his mouth and 

 chews it up again. The whole proceeding is most 



