1.] ANTECEDENTS. 11
thank my correspondents for the courteousness with which they replied to my very troublesome 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 questioning 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 anonymously, with the exception of one chapter in which the pedigrees of certain families are given.