44 



THE AMEBIC AN NATURALIST [Vol. XLIX 



we may be dealing with a system of multiple allelomorphs. No 

 two of the types when mated together give a third in F^, and, 

 unless one or both carry a recessive in heterozygous form, any 

 two types give a 3 : 1 ratio in F 2 , or 1:1 on back-crossing to a 

 recessive. The four patterns involved seem, from the descrip- 

 tions, to fall roughly into a series in the order striped, moricaud, 

 normal, and plain. That is to say, the second two are rather 

 intermediate in appearance between striped and plain. Al- 

 though I believe any arguments as to the nature of genes which 

 are based on the appearance of characters are open to very seri- 

 ous objections, it must still be admitted that the different char- 

 acters involved in a case of multiple allelomorphism are gener- 

 ally of the same sort. 4 



On the chromosome view, if the genes just discussed are allelo- 

 morphs they occupy identical loci in homologous chromosomes. 

 If they are not allelomorphic but closely linked, they occupy 

 different but closely opposed loci in homologous chromosomes. 

 In either case, any combination of them should give approxi- 

 mately the same linkage to the Y-y pair of genes, which occupy 

 a locus in the same chromosome, but some distance away. The 

 linkage of the striped-normal, striped-plain, and 1 moricaud-plain 

 combinations with the Y-y locus appear from Tanaka's data to 

 be in fact about the same, though the data on the first (striped- 

 normal) are the only ones sufficiently large to be very significant. 



A. H. Sturtevant 



Columbia University, 

 October, 1914 



THE INFLUENCE OF POSITION IN THE POD UPON 

 THE WEIGHT OF THE BEAN SEED 

 In a note on the pure line problem Belling 1 has emphasized the 

 significance of position in the pod as a factor in determining the 

 weight of the bean seed. Since this point in his paper seems to 

 have attracted some attention among those interested in genetics, 

 it may not be out of place to call attention to a series of quanti- 

 tative determinations of the intensity of the relationship 2 and to 

 illustrate the results secured. 



If one numbers the successive ovules of the pod from 1 up, 

 * I have discussed this aspect of the matter briefly in another paper 

 (Amer. Nat., XL VII, 1913, p. 237). 



1 Belling, J., "Selection in Pure Lines," Amer. Breed. Mag., 3: 311-312, 

 1912. 



2 Harris, J. Arthur, "A Quantitative Study of the Factors Influencing the 



