100 SEA-SIDE STUDIES. 



our is as unchangeable as the diverse impressions of 

 the animal. It consists of a complicated system of 

 globules of various colours, red, brown, and yellow, 

 placed under the first layer of the epidermis. These 

 globules have each a pupil which contracts and dilates, 

 forming now a large irregular spot, and now diminish- 

 ing to a mere point. It is easy to understand, there- 

 fore, how the animal which, when the globules are 

 dilated, is of a dark colour, becomes almost white 

 when these globules are contracted. The contractabil- 

 ity of these globules tlierefore always depends on the 

 will of the animal ; and he varies his colour from 

 brown to white with remarkable vivacity according to 

 his own will." * 



Attention is called to this passage, as one among 

 the numerous illustrations of that serious want of a 

 doctrine to guide investigations, w^hich is the greatest 

 obstacle Zoology has now to contend with. The mass 

 of facts which has been accumulated is of astonishing 

 extent ; but the philosophy which should be evolved 

 from them, which should co-ordinate them, and serve 

 as a torch to guide zoologists in all inquiries, is still in 

 the most meagre condition. To confine ourselves, for 

 the present, to the case before us, is it not remarkable 

 that a man so eminent as M. d"Orbigny should have 

 written, and some other men acquiesced in, a passage 

 so preposterous as the one just cited? Where was the 

 biological philosophy which could conceive the contrac- 

 tility of pigment globules as dependent on the "will of 



* D'Orbignt : Mollusques vivanU etfossiles, p. 113. 



