IX 



appearances are not really new, but clue to the reappearance 

 of extremely ancient and, as it were, " buried " characters. 

 This was also Mr. Gerould's opinion, for he wrote in the 

 letter of which part has been already quoted :— 



" ' New ' mutations in my dialect are merely inheritable 

 discontinuous variations, new to science. I agree with you 

 entirely as regarding the two (blue-green and olive-green) 

 as ' buried recessive characters ' brought to light by inbreeding. 

 Many of the mutants of DrosopJiila are of this sort. Geneticists, 

 it seems to me, are coming to use the term mutation without 

 reference to the time when the process behind it first occurred, 

 and in a sense quite different from that used by De Vries. I 

 believe that such intensive inbreeding of almost an)^ insect 

 as has been employed with Drosophila will bring out a similar 

 array of ' mutations.' 



" My olive-green strain probably came from a male imported 

 from N.Y., close to the range of eurytheme [Boisd.]. It may 

 well be the ' revival of an ancient character,' of which you speak, 

 derived from that wide-spread species from which philodice, 

 I think, has sprung." 



On Nov. 29, 1921, shortly before his death. Dr. Chapman 

 wrote to Prof. Poulton on the same subject, enclosing a 

 statement of his views on " factors," thus referred to in the 

 accompanying letter : — ■ 



" I have been turning over in my mind for some years an 

 idea concerning ' factors,' that I am afraid I shall never have 

 time or energy to follow up more fully. I have tried to describe 

 it briefly, and enclose the results for your consideration. In 

 looking it over I fear brevity means obscurity. I do not know 

 whether any one has elaborated the same idea. 



" It is, that any particular factor in any particular species 

 (plant or animal) has a quasi-independent existence, and can 

 vary and be selected, etc., apart from all the other factors, of 

 which the germplasm consists. That Mendelian factors arise 

 in this way ; — as a subsidiary point, that when any factor is 

 divided into two races (Mendelian or still miscible) one of 

 these (either?) may recede much deeper than a Mendelian 

 recessive, but still exist and be capable of declaring itself on 

 occasion." 



