370 



or yet again, if one observe the strange effect of dimate on color ^ 

 how, in one genus (say Stigmodera) by far the most richly-colored 

 (as well as largest) species are found in the cooler latitudes, while 

 the genus seems to decline in every way, becoming rarer, and 

 represented by smaller, less brilliant forms as one approaches the 

 tropics, while in another group (say the Lamiides) the case is ab- 

 solutely reversed; when one takes all these and many other such 

 remarkable facts into account, it is impossible to doubt that 

 there is a reason for their being facts written, it may be in 

 geological, it may be in che^nical characters, and its record stored 

 deeply in the bowels of the earth, or floating in the atmosphere, 

 or on the ocean, awaiting the day when science shall be strong 

 enough and wise enough to seize and read that record. 



I think it is not passing the limits of what we are justified in 

 asserting, to say that for every variety of structure in every 

 species there is a reason (at least conceivably discoverable). Such 

 an assertion is not based upon any particular view of the nature 

 of species. On the theory of their immutability it may be 

 assumed that the Creator of the various forms of life endowed 

 each form with characters suited to what its needs would be, and 

 therefore resulting (even though only by a7iticipationJ from its en- 

 vironment. On any theory of development or natural selection, 

 each character would, of course, necessarily be the direct resultant 

 oi some feature or features in the environment by means of 

 which its development had been provided for. 



If this be accepted as an axiom, and it really appears to me 

 that it ought to be so accepted, there opens out a field of operations 

 bewildering in its vastness in which one branch of natural science 

 may be foreseen to throw light upon another, in which the prob- 

 lems and perplexities and difficulties of one class of workers may 

 be solved by another class who are investigating what seems to 

 be a totally disconnected subject, and in which some wide-reach- 

 ing truth may be brought to light by the observance of some 

 character or phenomenon in some sphere of study that for one 

 reason or other appears among the least likely to be productive 

 of important conclusions. 



Thus, it is probable that if the reasons were adequately known 

 of the prevalence of given generic characters in given localities, 

 they would throw a flood of light upon geology ; and vice versa 

 if the geological history (in the widest sense of that expression) 

 of a particular country were known in all its details with abso- 

 lute accuracy, we should be able to specify without much diffi- 

 culty the reason why the development of the fauna of that 

 country tended in a given direction. 



Indeed, it has always appeared to me one of the strongest of 

 .arguments for the truth of the theory of development (which 



