FIRST PUBLISHED ESSAY. 67 



driven to try and catch more hares, and hence would 

 be selected in the direction of speed and sharp eye- 

 sight. " I can see no more reason to doubt that these 

 cases in a thousand generations would produce a 

 marked effect, and adapt the form of the fox or dog 

 to the catching of hares instead of rabbits, than that 

 greyhounds can be improved by selection and careful 

 breeding." So also with plants having seeds with 

 rather more down, leading to wider dissemination. 

 Darwin here added this note : " I can see no more 

 difficulty in this, than in the planter improving his 

 varieties of the cotton plant. C. D. 1858." . 



Then follows a brief sketch of sexual selection and 

 a comparison with natural selection, and the con- 

 clusion is reached " this kind of selection, however, 

 is less vigorous than the other ; it does not require 

 the death of the less successful, but gives to them 

 fewer descendants. The struggle falls, moreover, at a 

 time of year when food is generally abundant, and 

 perhaps the effect chiefly produced would be the 

 modification of the secondary sexual characters, 

 which are not related to the power of obtaining food, 

 or to defence from enemies, but to fighting with or 

 rivalling other males." 



The second section was entitled " Abstract of a 

 Letter from C. Darwin, Esq., to Professor Asa Gray, 

 Boston, U.S., dated Down, September 5th, 1857." To 

 this letter Darwin attached great importance as a 

 convenient and brief account of the essentials of his 

 theory, written and sent to Asa Gray many months 



