f)!l,S Toyama, On certain characteristics of the Silk-worm etc. 



The first or homozygous dominant white mated with yellow 

 gives all white F 1? the second or heterozygous white mated with 

 yellow, a mixed F 1? consisting of yellow and white in equal propor- 

 tions, and, lastly, the third or homozygous recessive mating, all 

 yellow F r Hence in such white-yellow matings, F 1 will consist of 

 three kinds of offspring. 



As the composition of all white F 1 is WY, the F 2 will be 3 

 whites: 1 yellow, while all yellow F i whose composition is wY will 

 give diametrically opposite results; namely 1 white: 3 yellows in 

 F 2 . The posterity of these series will follow the mono-hybrid prin- 

 ciple, in the former, white always behaving as dominant, and in 

 the latter, as recessive. 



In the series in which the F 1 is a mixed offspring of white 

 and yellow, both white and yellow segregate again into their compo- 

 nents and thus the phenomena of inheritance seem to be quite 

 inconsistent with Mendelian principles, if we considered them to 

 be a case of Monohybrid back-crosses, 1 W : 1 Y. As the formula 

 shows, however, both of them are heterozygous, and therefore their 

 segregation in F 2 is consistent with Mendelian principles, and the 

 white is dominant in the white series, and recessive in the yellow 

 series. 



Thus the order of inheritance of mixed white mated with 

 yellow will be represented as below: 



Mixed White X Yellow. 



(1.) ( 2 -) 



F, All W (1 W : 1 Y) 



F, (3 W : 1 Y) (3 W : 1 Y) (1 W : 3 Y). 



(3.) 

 F, All Y 



F, (1 W : 3Y). 



(4.) 



(F t white X ^ yellow.) 

 F, (1 W : 1 Y) 



F 2 '(3 W : 1 Y) ' '(1 W : 3 Y). ' 



The results of experiments made by Coutagne and Kellogg 

 may come in the same category. We shall now quote their results 

 graphically summarized from their original papers 6 ). 



6) Coutagne, G. - - Recherches expe'rimentales sur 1'he'redite chez les vers a 

 soie. 1902. 



Kellogg, V. L. - - Inheritance in silk- worms. 1908. 



