no 



THE LIFE OF CRUSTACEA 



(Fig. 40), one of the Spider Crabs (Oxyrhyncha 

 which is found in the Indian and Pacific Oceans. 

 In this little Crab the carapace is flat, and is extra- 

 ordinarily variable in form. In most of the males it 



is triangular in outline, but 

 in most of the females and 

 in some males it is broadened 

 by leaf-like expansions of the 

 side edges. Borradaile has 

 pointed out that these broad 

 individuals are usually found 

 among the sea-weed Hali- 

 meda, and that they closely 

 resemble the fronds of this 

 weed in form and in their 

 FIG. 4 o A, A PIECE OF A greenish colour. 



TROPICAL SEA-WEED A nnmhprnf Trnctarpa ar* 



(Halimeda) ; B, A CRAB A numb ' 



(Huenia proteus) WHICH known to possess a chame- 



LIVES AMONG THE 



FRONDS OF Halimeda, AND leon-like power of changing 



CLOSELY RESEMBLES THEM . i /-m 



IN FORM AND COLOUR, their colour. The mechanism 



chan S e is ef - 



fected is similar to that found 



in other animals, such as fish and frogs, which have 

 the same power. The pigment which gives its colour 

 to the animal is lodged in microscopic star-shaped 

 bodies known as chromatophores, lying for the most 

 part just below the skin. Each chromatophore 

 consists of a central body from which a number of 

 branching filaments radiate. The pigment may con- 



