44 FIFTY YEARS OF DARWINISM 



descent with modification of species, by no means 

 implying change by large and sudden steps as in 

 the usual modern acceptation of the term. In- 

 deed, the words " mutable," " mutability," and 

 their opposites have never been employed with 

 the special significance now attached to " muta- 

 tion." Every one believes in the mutabihty of 

 species, but opinions differ as to whether they 

 change by mutation. 



It is a mistake to suppose that Darwin did not 

 long and carefully consider large variations, or 

 " mutations," as supplying the material for evo- 

 lution. Writing to Asa Gray as early as August 

 11, 1860, he said ^ of great and sudden varia- 

 ation: — 



" I have, of course, no objection to this, indeed it 

 would be a great aid, but I did not allude to the subject, 

 for, after much labor, I could find nothing which satis- 

 fied me of the probability of such occurrences. There 

 seems to me in almost every case too much, too complex 

 and too beautiful adaptation in every structure to 

 believe in its sudden production." 



In the twenty years between 1860 and 1880 we 

 find that Darwin was continually brought back 

 to this subject by his correspondents, and by re- 

 views and criticisms of his work. Scattered over 



some suspicions that it was not quite correct, and yet I do not 

 yet see my way to arrive at any better terms. It will be years 

 before I publish, so that I shall have plenty of time to think 

 of better words. Development would perhaps do, only it applied 

 to the changes of an individual during its growth." More Letters, 

 I, p. 60. 

 » Life and Letters, II, pp. 333, 334. 



