5O THE MEANING OF EVOLUTION 



Still others will be differently colored. They might be 

 arranged to show a considerable gradation between 

 the lightest and the darkest of the group, though 

 there may not be anywhere in the row a considerable 

 gap. It is variation in animals of the same parentage 

 and same surroundings which in the mind of Mr. 

 Darwin made evolution possible. He always favored 

 the idea that it was the continuous accumulation of 

 these small variations that finally produced the pro- 

 found changes which mark the new species. He ad- 

 mitted the possibility of the occasional appearance of 

 those more distinct leaps in variation on which the 

 present school of mutationists so strongly insists ; but 

 he believed them to be less influential, in the general 

 trend of evolution, than the slower but much more fre- 

 quent variations. 



One of the most complicated and perplexing prob- 

 lems in the biology of to-day is the question of the 

 origin of these variations. It is quite as hard to 

 understand as is the method by which animals pro- 

 duce their own kind. No problem is being more 

 earnestly studied. Suppositions we have in consider- 

 able number, and two of these at least may reasonably 

 be mentioned. We will consider first the less certain 

 theory. There is nothing in the egg that in the re- 

 motest degree resembles its parent. The old idea that 

 every acorn had in it a miniature oak which only 



