are the youngest members of large families. Bohannon found that youngest children tend to be exceptional and abnormal, precocity being a specially prominent trait among them. Among the socially degenerate classes Dugdale found first-born and last-born prominent, the former tending to be criminals, the latter paupers.
Whenever it has been possible I have noted the age of the father at the birth of his eminent child. It has been possible to ascertain this in 204 cases, and the data thus obtained may be considered as fairly free from fallacy, so far as the biographical mind is concerned. The range of age is considerable, from 15, the age of Napier of Merchiston's father at his birth, to 79, the age of Charles Leslie's father, the period of potency in the case of the fathers of persons of eminent ability thus ranging over 64 years. The 204 cases may be grouped in five-year age-periods as follows:
| Under 20 | 20-24 | 25-29 | 30-34 | 35-39 | 40-44 | 45-49 | 50-54 | 55-59 | 60 and over |
| 1 | 7 | 22 | 54 | 41 | 33 | 24 | 9 | 7 | 6 |
These figures run in a fairly smooth and regular way, and I believe that they are very noteworthy and significant. It will be seen that 30-34 is the most frequent age of fatherhood, and that while there are very few cases of fatherhood during the ten preceding years, when sexual vigor is at its height, the majority of eminent persons have been begotten by fathers who had already passed this age of most frequent fatherhood. This result is the more significant when we remember that we are chiefly dealing with the upper social classes (for it is in their cases that these facts are most easily ascertained), and that we must exclude the quite modern tendency to retardation of the age of marriage. I have no figures of the age of fatherhood among normal subjects quite fairly comparable with those here presented. The significance of the age of fatherhood has been chiefly studied, so far as I am aware, by Marro in North Italy, and we cannot assume that the conditions are there quite the same. Marro divided the fathers of his normal subjects into three classes: (1) Below 25 years of age, a stage of immaturity; (2) from 26 to 40 years of age, a stage of maturity; (3) over 40 years of age, a stage of decadence. He found that 8.8 per cent, fathers of normal subjects belonged to the first group, 66.1 to the second class and 24 to the third. The corresponding figures for the fathers of the persons of eminent ability concerned in the present inquiry are 3.9, 57.3 and 38.7. Whatever the value of this comparison, there can be little doubt that an abnormally high age prevails among the fathers of our eminent persons. I have only been able to ascertain the age of the mother in 40 instances. In these cases it is distributed as follows:
| Age of mother | 21-24 | 25-29 | 30-34 | 35-39 | 40-44 | 45-49 | 50 |
| Number of cases | 8 | 13 | 8 | 5 | 4 | 1 | 1 |
Except for the one very unusual instance at 50 (Dibdin's mother),
