o 



S>2 BIOLOGY AND ITS MAKERS 



cessfiil in this attempt, the fact that he undertook the task 

 places his contribution at the outset on a very high plane. 



The existence of variation as established by observation 

 is unquestioned. No two living organisms are exactly alike 

 at the time of their birth, and even if they are brought up 

 together under identical surroundings they vary. The varia- 

 tion of plants and animals under domestication is so con- 

 spicuous and well known that this kind of variation was the 

 lirst to attract attention. It was asserted that these varia- 

 tions were perpetuated because the forms had been protected 

 by man, and it was doubted that animals varied to any con- 

 siderable extent in a state of nature. Extended collections 

 and observations in field and forest have, however, set this 

 question at rest. 



If crows or robins or other birds are collected on an exten- 

 sive scale, the variability of the same species will be evident. 

 Many examples show that the so-called species differ greatly 

 in widely separated geographical areas, but collections from 

 the intermediate territory demonstrate that the variations 

 are connected by a series of fine gradations. If, for illustra- 

 tion, one should pass across the United States from the 

 Atlantic to the Pacific coast, collecting one species of bird, 

 the entire collection would exhibit wide variations, but the 

 extremes would be connected by intermediate forms. 



The amount of variation in a state of nature is much 

 greater than was at first supposed, because extensive collec- 

 tions were lacking, but the existence of wide variation is now 

 established on the basis of observation. This fact of varia- 

 tion among animals and ]j»lants in the state of nature is 

 unchallenged, and affords a good point to start from in con- 

 sidering Darwinism. 



Inheritance. — The idea that these variations are inher- 

 ited is the second point. But what particular variations will 

 be preserved and fostered by inheritance, and on what 



