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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 

 greenish colour. 



A number of Crustacea are 



Fig. 40 — A, a 

 Trop ical 

 {Halimeda) ; 

 {Huenia pro tens) 



LIVES AMONG THE 



Fronds of Halimeda, and 



CLOSELY RESEMBLES THEM 



IN Form and Colour. 

 Reduced. (After Borra- 

 daile.) 



Piece of a 

 Sea-weed 

 B, A Crab 



WHICH known to possess a chame- 

 leon-like power of changing 

 their colour. The mechanism 

 by which this change 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- 



