6 FACTORS IX VARIATION. 



The ■■ large body of evidence "' is now far more 

 impressive. In a notable work*, J. E. Adami states : — 

 ■■ To the worker in liacteriologv the hesitancy on the part 

 of biologists to accept environment as a most important 

 factor in oiiginating variation is almost incomprehensible." 

 Lat.r he adds (p. 161) : — ■" Individual variation is not 

 primarily due to any inherent tendency on the part of living 

 matter to vary. On the contrary, living matter is capable 

 of being railed according to its environment." 



Lloyd Morgan and others have restricted " variation "' 

 to differences arising germinally, whilst acquired 

 characteristics are called "' modifications,'' the former being 

 a product of natm^e, and the other of nurture. Archdall 

 Reid has shrewdly criticised these distinctions and has 

 shown that they cannot logically- be maintained. It might 

 almost be stated that a variation, in this sense, is a 

 modification so deeply rooted that the cause is obscure. 

 In any case, light is now being shed on the origin of 

 germinal variations. Lloyd Morgan suggests that plastic 

 modifications may pave the way for them. The exponents 

 of vitalism postulate potencies or entelechies in the germ 

 which they claim are the real factors of variation. But 

 this is but a confession of our ignorance of causes and is 

 a mixture of metaphysics and science. Professor E. W. 

 MacBride criticisesf the views of Driesch " in calling up 

 spirits from the void," and adds : — " We thus come to the 

 conclusion that for the present we may dismiss the 

 conce])tion of the entelechy from our minds as a A\orking 

 hypotheses and adopt instead the conception of organ- 

 forming substances "" One may appropriately 



add here Di-. J. S. Haldanes remark : — "' We neither need, 

 nor will have, any ghosts in physiology."'} 



There is still much controversy on the inheritance or 

 non-inheritance of acquired characteristics. It seems to 

 the ^\•riter that the arbitary distinction made between 

 somatogenic and blastogenic characteristics is due to our 



*.). (i. Adami : Medical Contribiitions to the Study of Evolution, 

 1918, p. lol. 



tE. W. MacBride, Rep. Brit. Assn., 191(i, p. 409. 



JJ. S. Haldane: The New Physiology, 1919. 



