January 22, 1904.] 



SCIENCE. 



153 



4 n. The third generation accords with the 

 assumption that the p parent has (D -{- B) 

 gametes, while the p parent in the third gen- 

 eration behaves as would one that had purely 

 dominant gametes. Unfortunately, the record 

 stops here. 



Struthers has given the following case of 

 polydaetylism in man: 



>X» 



I 



lOp 



3p 



pXt 



I 



III. 4n 



This result can be explained on the Men- 

 delian hypothesis by considering the original 

 pai-ent to have only D gametes; and that the 

 father was also polydaetyl. The offspring (I.) 

 are all p and purely dominant. In the first filial 

 generation D is crossed with B and the dom- 

 inant offspring have {D ■-{- B) gametes; when 

 one of these gametes of the second filial gen- 

 eration is crossed by B the product is DB -\- 

 BB (third generation). We should expect an 

 equal number of dominant and recessive indi- 

 viduals and we get them. If, on the other 

 hand, we calculate the proportion of abnormal 

 individuals in accordance with Galton's Law 

 we should get only 33 per cent, instead of the 

 actual 50 per cent. Mendel's Law here ac- 

 cords with the facts better than Galton's Law. 



These relations and the remaining descendants 

 are given in the accompanying diagram. 



This case differs from the preceding in the 

 small proportion of p's occurring in any gen- 

 eration. These small percentages can hardly 

 accord with Mendel's Law. 



Finally, we may consider some cases of 

 inheritance of deaf-mutism for records of 

 which we are indebted to Bell, 1884, Mem. 

 National Academy of Sciences, IL, pp. 179 

 and 208. 



I. 

 II. 



III. 

 IV. 



I]. 



iX» 



nXn 

 I 



dXf 



I 



dXd 



1 

 d 



dX^ 



±_ 



3d 



nXd 

 I 



d 



nX( 



nXc 



III. 2d id 



It seems impossible to regard either w or d 

 as recessive. If n is recessive how can d be 

 derived from two n parents as in Case A, 

 Gen. I. ? li d is recessive, how can 5 n come 

 from two d parents as in A, Gen. HI.? 



The conclusion of this communication is that 

 while Mendelian principles seem applicable to 



Another series is given by Struthers (1863) 

 in the Edinburgh New Philosophical Journal 

 for July. Mr. A. L., normal, married E. P., 

 who had six fingers on the left hand. They 

 had eighteen children, of whom one only was 

 abnormal, with six fingers on both hands. 



some cases of crosses between sports and the 

 normal species, there seem to be others where 

 neither Mendel's nor Galton's Law of Inherit- 

 ance holds. 0. B. Davenport. 

 Hull Zoologicai, Laboratory, 

 University of Chicago. 



