ii VIGOUR AND COLOUR 69 



a progeny is obtained, but the latter is deficient and 

 lacks vitality. 1 As a last proof of the relation between 

 vigour and colour, we may notice the fact that accord- 

 ing to many authors, among them Settegast, Heusinger, 

 and Wyman, animals deeply coloured, animals of 

 black coats for instance, are well able to withstand 

 the influence of poisonous plants, which kill others 

 less coloured. There thus seems to exist a positive 

 relationship between vigour and colour, and this 

 cannot be wondered at, since colour is the result of 

 chemical processes which are carried on in the organ- 

 ism, and since this metabolism certainly varies in in- 

 tensity and rapidity in different individuals. Other 

 agencies, which may operate on vigour, exert an 

 influence on colour ; light is such an agency, but facts 

 seem somewhat contradictory, and we cannot wonder 

 at this when we consider that while light varies, other 

 influences, such as heat, may not vary, or may vary 

 in a different direction. The climate is also operative 

 although we can certainly not give a precise defini- 

 tion of this term and an interesting case is that of a 

 herd of Dishleys living in the vicinity of the sea, in 

 France. These Dishleys were always spotted on the 

 face and ears, and had large black spots which rather 

 discouraged buyers. The owner said these spots were 



1 Tissernnd : fitudes economiqiies sur le D<nte'>wfc, le Hohtein, ft It 



Slesivig. 



