CONTRACTILITY OF COLOUR-SPECS. 95 



yellow, placed under the first layer of the epidermis. These 

 globules have each a pupil which contracts and dilates, form- 

 ing now a large irregular spot, and now diminishing to a 

 mere point. It is easy to understand, therefore, how the 

 animal which, when the globules are dilated, is of a dark 

 colour, becomes almost white when these globules are 

 contracted. The contractability of these globules therefore 

 always depends on the will of the animal ; and he varies his 

 colour from brown to white with remarkable vivacity accord- 

 ing 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, which 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 con- 

 fine 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 bio- 

 logical i^hilosophy which could conceive the contractility 

 of pigment globules as dependent on the "will of the 

 animal ;" especially when such a leap in logic had to be taken 

 as is taken at the "therefore?" Physiologists are, indeed, 

 extremely facile in their admission of " the will " to explain 

 ■what they do not understand ; but v>' e must marvel that 



* D'Orbigny: MoUusqv.es vivants etfossilcs, p. 113. 



