56 



THE STUDY OF ANIMAL LIFE CHAP. 



Profs. Gamble and Keeble have studied the extra- 

 ordinary power of colour-change in the Msop prawn 

 (Hippolyte varians), which takes on the colour of its 

 surroundings through a wide range (red, yellow, blue, 

 orange, olive, violet, brown, green) both when young 



6 



FIG. 11. CHROMATOPHORES. 



A, a group 

 skin of a fish. 



of eight amosboid 

 (After Ballowitz.) 



pigment-cells (chromatophores) in the 

 They are fully expanded, sending out 

 ' 



filamentous processes (pseudopodia) in'all directions. A change of light 

 may bring about their contraction, and the lower figure (B) shows the 

 same group of eight cells contracted. Thus the colour changes. Black, 

 yellow, and red chromatophores are common in fishes. The silveriness 

 is mainly due to spangles of a waste product (guanin) enclosed in special 

 cells (iridocytes). The fine markings on the scales often enhance the 

 coloration, producing for physical reasons a sort of metallic or iridescent 

 brilliance. 



