ORGAXIC EVOLUTION — THE FACTORS 109 



has been inheritance of acquired chai-actera or there 

 has been no evolution." 



Put shortly his arguments are as foUows: lu the 

 individual increased functional activity in any structure 

 is followed, generally speaking, by an increase in the 

 size of that structure; this increase of functional 

 activity and size puts a strain on, and is followed by a 

 proportionate increase of activity and consequently of 

 size in many structures co-ordinated with the first; 

 these latter cheinges are the cause of changes in yet 

 other structures ; till, if the initial change be sufficiently 

 important, the whole organism is co-adaptively modified. 

 Now if acquired variations are transmissible, it is easy 

 to understand how these acquired co-adaptive changes, 

 dependent on functional activity, on use, accumulated 

 during generations, may result in co-adaptive evolution 

 of the most far-reaching kind in all the thousand 

 co-ordinated parts of a complex and heterogeneous 

 animal — e.g. mammal. But if they are not trans- 

 missible, by what means can we account for co-adaptive 

 evolution? How can we explain the fact that a 

 thousand structures are modified in the moose, the 

 elephant, and the man, in obvious co-adaption to 

 changes in the horns, the tnmk, and the fore Kmbs 

 respectively? For if we suppose that only inborn 

 variations are transmissible, we must suppose that all 

 the thousand structures varied favourably simultane- 

 ously and proportionately, and to suppose this is to 

 suppose that which is incredible. 



For instance, if during the evolution of the great 

 horns of the moose an animal varied spontaneously in 

 that he had larger horns than the ordinary, it is highly 

 unlikely of the thousand structures, the evolution of 

 which has been concomitant with and co-adaptive to 

 the evolution of the horns, that aU should have varied 

 favourably, and if they did not the &vourable variation 



