-304 WORK ON 'MAN.' [1870. 



me and ponder over. To answer it would require at least 

 200 folio pages ! If you could see how often I have re-written 

 some pages you would know how anxious I am to arrive as 

 near as I can to the truth. I lay great stress on what I know 

 takes place under domestication ; I think we start with 

 different fundamental notions on inheritance. I find ii is 

 most difficult, but not I think impossible, to see how, for in- 

 stance, a few red feathers appearing on the head of a male 

 bird, and which are at first transmitted to both sexes, could 

 come to be transmitted to males alone. It is not enough that 

 females should be produced from the males with red feathers, 

 which should be destitute of red feathers ; but these females 

 must have a latent tendency to produce such feathers, other- 

 wise they would cause deterioration in the red head-feathers 

 of their male offspring. Such latent tendency would be 

 shown by their producing the red feathers when old, or dis- 

 eased in their ovaria. But I have no difficulty in making the 

 whole head red if the few red feathers in the male from the 

 first tended to be sexually transmitted. I am quite willing 

 to admit that the female may have been modified, either at 

 the same time or subsequently, for protection by the accumu- 

 lation of variations limited in their transmission to the female 

 sex. I owe to your writings the consideration of this latter 

 point. But I cannot yet persuade myself that females alone 

 have often been modified for protection. Should you grudge 

 the trouble briefly to tell me whether you believe that the 

 plainer head and less bright colours of ? chaffinch,* the less 

 red on the head and less clean colours of ? goldfinch, the 

 much less red on the breast of ? bull-finch, the paler crest of 

 golden-crested wren, &c., have been acquired by them for 

 protection. I cannot think so any more than I can that the 

 considerable differences between ? and $ house sparrow, or 

 much greater brightness of $ Parus cceruleus (both of which 

 build under cover) than of ? Parus, are related to protection. 

 I even mis-doubt much whether the less blackness of $ black- 

 bird is for protection. 



* The symbols $ ? stand for male and female. 



