INTKODUCTOEY. 1 1 



they must have some explanation, which may not have been 

 forthcoming. 



A flagrant instance of non-adaptive coloration is the green 

 tint of the bones in the iishes Belone, Protopterus and 

 Lepidosiren, in the amphibian Pseudis and in a lizard. This 

 green colour is due to the presence of vivianite. 



These apparent anomalies can, however, be regarded from 

 another point of view: it cannot be too often or too strongly 

 urged that we are living now among changes in the organic 

 (and inorganic) world just as marked as they were formerly; 

 perhaps even more marked, for the number of species must 

 be greater now than in the very early periods of the world's 

 history; hence competition is keener. It is therefore not 

 surprising to find, among forms that appear to be " in harmony 

 with the environment," others that have not been able to move 

 with the times, or that are actually in process of moving. 



Constancy of Coloiation. 



It has been urged that the constancy of animal colour 

 indicates utility ; domestic animals, it is said, are subject to 

 great variability, which is not seen in their wild relatives; the 

 reason for this is supposed to be the elimination of such 

 varieties among the wild animals. They occur in them just 

 as much as in the domesticated forms, but these varying indi- 

 viduals do not reach matuiity, since they are not so suited to 

 ■cope with the conditions of their natural existence. 



There are, however, a number of facts that must be considered 

 in relation to this question. Firstly, most of our domestic 

 animals have been domesticated for a long time; so long is 

 this time that in many cases their origin is lost in the obscurity 

 of the past. Who can say, for example, when the dog was first 



