!88 CAUSES OF VARIATION 



will be the progeny of unbarred sires and out of dams once mated 

 with barred sires for other offspring. This smallest portion, get- 

 ting its bars not by direct descent but by reversion^ will most 

 likely be erroneously considered to have derived them from the 

 barred male not their sire. The same is true of other markings, 

 and on such evidence as this the theory of telegony has been 

 built up, and, so far as proof goes, it rests on no better founda- 

 tion as yet. In order to secure evidence amounting to proof, it 

 is necessary to examine large numbers involving both positive and 

 negative evidence, in order to secure trustworthy averages. When- 

 ever this has been done the theory of telegony fails of support. 



Telegony in man. The statistical method has been applied by 

 Pearson 1 in the case of man. He, together with Galton, pos- 

 sesses data covering hundreds of individuals in English families. 

 He reasoned that if the sire exerts a permanent influence upon 

 the dam, tending to assert itself in all future offspring, then this 

 influence must be in a sense cumulative, so that the younger sons 

 in the family will tend to resemble the father slightly more than 

 will the older sons, conceived before such influences have become 

 established. 



His study covered 385 brother brothers and 450 sister sisters, 

 taken two and two. In some instances there was considerable 

 difference in ages, and in others they were successive children. 

 His data covered both height and arm length, and after making 

 the usual allowances for sex and age Pearson concludes that, so 

 far as these characters are concerned, "no steady telegonic 

 influence exists." 



Again, the many successive marriages of both colored and 

 white women to men of opposite color should afford numerous 

 examples of telegony were it a consequential force in heredity. 



Scientific objections to the theory of telegony. If telegony 

 exists, its influence over hereditary characters must be explained, 

 so far as present knowledge goes, in one of three ways : ( i ) some 

 effect upon the tissues of the female such as will influence 

 future ova in their maturation or the embyro in its development ; 

 (2) something like a partial fertilization of immature and unde- 

 veloped ova, in such a way as to influence their character at 



1 Proceedings of the Royal Society, LX, 273. 



