Toyama, Mciidcl's lawa of heredtiy as applied to the silk-worm crosses. 823 



The proportion between the form a and ß is not so constant 

 as in the case of plants experimentell by Mendel, Correns, De 

 Vries, Tschermak and others. 



Of the form B, phenomena of segregation similar to those 

 observed in the third generation are repeated in subsequent gene- 

 rations when similar ones are bred together. 



The following table will serve to illustrate the phenomena of 

 the segregation of their parent-characters in the offspring: 



•Whites" X "Yellöws". 



Cross generation : 



The first all yellows. 



The second 75°/ yellow 



+ 



2r>"/ white. 



Some of offspring 

 uniform yellow 



Some of offspring 

 consisting of 



White (25 u / ) and Yellow (75 ' 



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c 



If we compare our results with those obtained by Mendel 

 and others in plants, we easily see that both agree very well except 

 in the two points mentioned below: 



The first consists in this that in plants when a dominant cha- 

 racter is once separated from a hybrid parent as a uniform brood, 

 it remains constant throughout subsequent generätions, while with 

 silk-worm it is not so, in as Jülich as the yellow form, once sepa- 

 rated as a uniform offspring, sometimes produces a mixed offspring 

 subsequently. The second point of the difference is that the pro- 

 portion between pure and hybrid dominant forms which appears 

 in the third generation does not remain constant. 



This discrepancy may be due to the following causes : 



In the second cross generation, as Mendel taught us, there 

 are two kinds of dominant forms, one pure dominant or D, another 



21* 



