380 



The Journal of Heredity 



proof of hereditary influence; even half visibly affected. Extending this ]jrin- 



a dozen or a dozen may be of no sig- eiple, it is easy to see that a boy might 



nificance. There are two ways in inherit some traits from his mother, 



which we can analyze genealogical data which his father wholly lacked, and that 



to deduce biological laws: one is based a daughter might similarly receive 



on the application of higher mathe- exclusive traits from her father. I must 



matics to mass statistics, and needs some say that sex-linked heredity in the 



hundreds of cases to be of value; the himian race has so far been definitelv 



other is by pedigree-study, and needs proved only in regard to color-blindness, 



at least three generations of pedigree, hemophilia, and a few other abnormal 



usually covering numerous collaterals, conditions; Init with the cooperation of 



to offer any certain results. Not all the genealogists it is probable that we 



the findings announced even by ]3ro- will find this condition, as important as 



fessionaleugenists have met one or other it is interesting, to prevail more widely, 



of these requirements, and to the extent The problem of the inheritance of 



in which they have fallen short, they fecundity can obviouslv be settled only 



are being discredited. It is not to be through ' proper genealogical material, 



supposed that anyone with a sufficiently It is known that fecunditv is to some 



complete record of his own ancestry extent an inherited character, although 



would necessarily be able by mspection doubtless affected in Man largely by 



to deduce from it any important contri- outward circumstances. The voluntary 



bution to science. But if enough com- limitation of births, which has become 



plete family records are made available, ^o widespread during the last genera- 



the professional genetist can be called tion, of course complicates the studv of 



into cooperation, can supplement the ^h^g subject, but there is nevertheless 



human record with his knowledge of ^oom for much work of a distinctlv 



the results achieved by carefully con- practical kind. Obviously, one of the 



trolled animal and plant breedmg and ^^^-^^^ ^^ improve the general 



between them, the genealogist and the ^^ ^^ ^^^ ^^^^ ^^^^^^ ^^ ^^ ^^^^ 



eugenist can m most cases arrive at the u- x. f ^■^. • ^.u ■ *. ^ 



. ^u n^-u ^ u^ i-t, • r^u !-• t- ^ high iccunditv m the superior stocks 



truth. 1 hat such truth IS 01 the highest j , . ' .. . ^. • r • 



•_ . . r -1 J 11 and low lecundity m the interior ones, 



importance to anv lamilv, and equally , . ,, .J . .^^ .. 



to society as a whole, must be evident. ^^ ^^ equally obvious that if fecundity is 



associated with mienonty — with teeble- 



SEX-LiNKED INHERITANCE mindcdncss, for cxamplc.-that disastrous 



The whole question of sex-linked results will ensue if Nature is allowed to 



inheritance depends for its solution on "take its course." The genealogist 



the extension of genealogical material, can contribute indispensable material 



It is often said that sons take after their for this study, and for the general study 



mothers, while daughters tend to resem- of the birth-rate in various sections of 



blc their fathers. The Arabs and the community at various periods — a 



Hebrews put the same idea a little study which is the very foundation of 



differently, that a son tends to resemble applied eugenics. 



his maternal uncle. Is there anything Frederick S. Crum's work" on i)u])- 



in these ideas? In a small way, there ijshed genealogies of New l<:ngland 



is no mystery about it; we know that families shows what can be done in this 



certain hereditary traits are scx-hnked- li,,^ p^^^^ ]^i, material, C^-um was 



that they are earned by one .sex but ^^^^^ ^„ ,^ ^^^ f,^,. 12.722 wives, and 



appear in the other. Thus, it is^ rare ^c found that xhv number of children 



to find women who are color bhnd, but ^^,.^^ ^^^^ decreased as follows : 



a woman who docs not show this defect __ 



herself may have inherited it from her isoo is4<) 4 94 



father, who was visibly affected, and ikso-lSM^ 3 47 



transmit it to her sons, who will also be 1870-1879. . '..'....'.'........ 2. 77 



" Crum, Frederick S. The Decadence of the Native American Stock. Quarterly Piil>. .\nuT- 

 ican Statistical Assn., XIV, n. s. 107, pp. 215-22.S. Sept., I'>t4. 



