TRANSMISSION OF MODIFICATIONS 349 



matter, that they are at work, and it is here that races are 

 enriched, almost miraculously, with new and valuable endow- 

 ments, not frequently and freely, but occasionally and spar- 

 ingly. These are the free gift of nature, arising, so far as we 

 can now see, spontaneously, but due, as we firmly believe, to 

 definite influences at work within the germ, which is the avenue 

 of all transmissible variations. 



Remembering, then, that all influences that affect the germ 

 will give rise to variations, we come now to the direct question 

 of the chapter, Are the modifying effects of external influences 

 transmitted ? or does each generation begin anew, unhampered 

 and unhelped by the direct effects of previous environment, 

 whether favorable or unfavorable ? 



The main question. This is an exceedingly important matter ; 

 indeed, no other question in all evolution is of such immediate 

 and far-reaching consequence in thremmatology. This is because 

 the influences of environment are insidious and at the same 

 time well-nigh irresistible. If their effects are also transmis- 

 sible, they will become, like compound interest or any other 

 geometrical progression, strongly and rapidly cumulative, and 

 therefore tremendously powerful either for good or for evil. 



This is the old and hotly contested question of " inheritance 

 of acquired characters," better stated for our purposes in the 

 form, Are the effects of environment transmitted ? It is but 

 fair to warn the student that this is at once the most difficult 

 and the most complicated of all the questions of evolution, and 

 that not only must its study be critically conducted but the 

 student must be constantly mindful of certain fundamental 

 considerations, a few of which it will be well to note before 

 proceeding to the discussion of the main question. 



What is a deviation? What we call a variation, a devia- 

 tion, or a modification, is not, like a character, an entity that 

 can be transmitted. It is rather the degree to which a character 

 attains, as measured from the general mean or average of the 

 race as a whole. When we speak, therefore, of the trans- 

 mission of a variation or a modification, we mean literally the 

 transmission of the character as modified, either by internal or 

 external causes. 



