Davenport and Weeks : Inheritance of Epilepsy 27 



pose that the families of such strains as we have studied are 

 increasing faster than the population at large ? We do not know 

 the average size of fraternities in New Jersey. The census deter- 

 mination of " size of private family " is 4.4 for the state, which 

 would allow for 2 parents and 2.4 children ; but this gives a very 

 imperfect idea of the size of fraternities, because only children 

 at home are considered in the family, incomplete fraternities are 

 averaged with those fully finished, and there are other objections 

 that will readily occur to anyone. We would perhaps do better 

 to compare the size of our fraternities with those of a high social 

 status like those of Harvard graduates which average slightly 

 less than two children. For the better educated, more effective, 

 and mentally most advanced part of our eastern population the 

 average number of children of a pair of parents is probably be- 

 tween three and four. What is it in our special population ? A 

 count was made of 108 fraternities taken at random — the first 

 108 in the series fulfilling the following conditions : The members 

 of the fraternity were born (as far as it was possible to select 

 them) between i860 and 1900, ensuring the completion of the 

 family and at the same time bringing the families as close as 

 possible to the present. However, as was inevitable, some of the 

 families belong to an earlier decade (of the seventies or eighties), 

 when the number of children in a family was larger than now. 

 The average size of the fraternities counted is close to 5, and 

 the average number of the members surviving to maturity was 

 about four. All in all, the result indicates that the fraternities in 

 the strains to which epileptics belong are not very different in 

 size from those of the population at large. Even in the matings 

 of two feeble-minded persons the average number of offspring 

 of a single mating is only 4.4, but the total fecundity of the 

 mothers averages slightly higher than that. 



All fraternities with feeble-minded mothers yield an average 

 of 6 (6.05) children born. The average fecundity of the mothers 

 is (on account of double matings) somewhat greater than this. 

 All fraternities with epileptic mothers yield an average of 6 (6.04) 

 children born. We have calculated the average number of chil- 

 dren born to families with " normal " mothers as taken from the 

 tables. These are not always the latest complete generation but 

 this is usually the case. Here we get again the figure 6 (6.06). 

 There is thus a surprising agreement in the size of fraternities 



