XV THE RELATION OF FACTS TO THEORIES 315 



This is in outline Simroth's theory as to the 

 origin of colour. His paper contains also numerous 

 other suggestions which we cannot well discuss here. 

 In general, he appears to believe that pigments are 

 all related, that their development follows a definite 

 order, and that their origin is due to the properties 

 of protoplasm and the inherited stimuli of external 

 conditions, such as light and warmth. On these, 

 which he calls " inorganic " factors, he is inclined to 

 lay much stress, especially in such cases as the 

 colours of shells, in which he says there can be no 

 question of adaptation. 



The theory is interesting in spite of its vagueness, 

 and is included here because it is in many respects 

 typical of recent theories. As neither it nor the 

 other suggestions similarly based upon an inheritance 

 of the effects of environmental stimuli, have the ex- 

 tensive following possessed by the Natural Selectionist 

 theory, we shall return, before going further, to a 

 detailed discussion of the latter, beginning with the 

 familiar subject of mimicry. 



Criticism of Natural Selection 



The existence of colour resemblances between 

 widely separated organisms, and that explanation 

 of it which is implicit in the term Mimicry, have 

 recently become almost universally familiar. The 

 term in its present use was first employed by Mr. 

 Bates, and his suggestions were adopted by Darwin, 

 Wallace, and others, and have since been widely 

 accepted. Criticism has, however, never been want- 

 ing, and in a recent paper M. M. C. Piepers brings 



