THE FACTORS OP ORGANIC EVOLUTION. O 



how insufficient was the assigned cause. During their 

 growth, a deer s horns are not used at all; and when, 

 having been cleared of the dead skin and dried-up blood 

 vessels covering them, they are ready for use, they are 

 nerveless and non-vascular, and hence are incapable of 

 undergoing any changes of structure consequent on changes 

 of function. 



Of these few then, who rejected the belief described by 

 Professor Huxley, and who, espousing the belief in a 

 continuous evolution, had to account for this evolution, it 

 must be said that though the cause assigned was a true 

 cause, yet, even admitting that it operated through successive 

 generations, it left unexplained the greater part of the facts. 

 Having been myself one of these few, I look back with 

 surprise at the way in which the facts which were congruous 

 with the espoused view monopolized consciousness and kept 

 out the facts which were incongruous with it conspicuous 

 though many of them were. The misjudgment was not 

 unnatural. Finding it impossible to accept any doctrine 

 which implied a breach in the uniform course of natural 

 causation, and, by implication, accepting as unquestionable 

 the origin and development of all organic forms by 

 accumulated modifications naturally caused, that which 

 appeared to explain certain classes of these modifications, 

 was supposed to be capable of explaining the rest : the 

 tendency being to assume that these would eventually be 

 similarly accounted for, though it was not clear how. 



Returning from this parenthethic remark, we are con 

 cerned here chiefly to remember that, as said at the outset, 

 there existed thirty years ago, no tenable theory about 

 the genesis of living things. Of the two alternative beliefs, 

 neither would bear critical examination. 



Out of this dead lock we were released in large measure, 

 though not I believe entirely by the Origin of Species. 

 That work brought into view a further factor ; or rather, 



