i.] ANTECEDENTS. 11 



thank my correspondents for the courteousness 

 with which they replied to my very trouble- 

 some queries, the great pains they have taken 

 to be precise and truthful in their statements, 

 and the confidence reposed in my discretion. 

 Those of the answers which are selected for 

 statistical treatment somewhat exceed 100 in 

 number. In addition to these, I have utilized 

 several others which were too incomplete for 

 statistical purposes, or which arrived late, but 

 these also have been of real service to me ; 

 sometimes in corroborating, at others in ques- 

 tioning previous provisional conclusions. I wish 

 emphatically to add that the foremost members 

 of the scientific world have contributed in full 

 proportion to their numbers. It must not for 

 a moment be supposed that mediocrity is 

 unduly represented in my data. 



Natural history is an impersonal result ; I 

 am therefore able to treat my subject anony- 

 mously, with the exception of one chapter 

 in which the pedigrees of certain families are 

 given. 



