THE FACTORS OF OEQANIC EVOLUTION. 45 



relations between these actions and certain attributes 

 common to all members of the assemblage. Hence it is 

 inferable that on living organisms, which form an assem 

 blage of this kind, and are unceasingly exposed in common 

 to the agencies composing their inorganic environments, 

 there must be wrought two such sets of effects. There 

 will result a universal likeness among them consequent on 

 the likeness of their respective relations to the matters 

 and forces around ; and there will result, in some cases, the 

 differences due to the differential effects of these matters 

 and forces, and in other cases, the changes which, being 

 life-sustaining or life-destroying, eventuate in certain 

 natural selections. 



I have, above, made a passing reference to the fact that 

 Mr. Darwin did not fail to take account of some among 

 f these effects directly produced on organisms by surrounding 

 C inorganic agencies. Here are extracts from the sixth 

 edition of the Origin of Species showing this. 

 &quot; It is very difficult to decide how far changed conditions, such as of 

 climate, food, &c., have acted in a definite manner. There is reason to 

 believe that in the course of time the effects have been greater than can be 

 proved by clear evidence. . . . Mr. Gould believes that birds of the same 

 species are more brightly coloured under a clear atmosphere, than when 

 living near the coast or on islands ; and Wollaston is convinced that 

 residence near the sea affects the colours of insects. Moquin-Tandon 

 gives a list of plants which, when growing near the sea-shore, have their 

 leaves in some degree fleshy, though not elsewhere fleshy &quot; (pp. 106-7). 

 &quot; Some observers are convinced that a damp climate affects the growth of 

 the hair, and that with the hair the horns are correlated&quot; (p. 159). 



In his subsequent work, Animals and Plants under 

 Domestic ationj Mr. Darwin still more clearly recognizes 

 &amp;lt; these causes of change in organization. A chapter is 

 devoted to the subject. After premising that &quot; the direct 

 action of the conditions of life, whether leading to definite 

 or indefinite results, is a totally distinct consideration 

 from the effects of natural selection;&quot; he goes on to say 

 that changed conditions of life &quot;have acted so definitely 

 and powerfully on the organisation of our domesticated 



