32 INHERITANCE IN SILKWORMS, I 



very regularity only emphasizes more the reality of individual 

 idiosyncrasies in such cases of reversed dominance. 



While white cocoon color is in most race crossings recessive in 

 character, it is, as already pointed out, not so in all crossings of white 

 and colored cocoon races. For example Bagdad race (white cocoon) 

 seems to be an especial vigorous or potent race in race crossings, the 

 white cocoon color being frequently dominant. Examples of this 

 have already been given. In addition Italian White (white cocoon) 

 crossed with Galbin Italiano (salmon-yellow cocoon) gives young all 

 spinning white cocoons and in F 2 lots the two colors segregate in 

 Mendelian proportions. In these crossings we have examples (asked 

 for by Bateson in his summing up of the "progress of genetics since 

 the rediscovery of Mendel's papers," p. 389, Progressus Rei 

 Botanicae, vol. i, 1907) of two whites producing a color. That is the 

 color is carried germinally through an all white F x to appear in F 2 . 



In some matings with this same Galbin Italiano salmon-yellow 

 cocoon race a reversal of the above described condition occurred. For 

 example Galbin Italiano crossed with Bagdad (in many crossings a 

 prepotent race and almost always stronger than Japanese White) 

 showed in F x a dominance of the salmon-yellow cocoon color which in 

 F 2 lots split in Mendelian proportions. 



Despite the inconsistencies in dominant-recessive relation between 

 the cocoon color exhibited in the foregoing data the faithfulness to the 

 alternative character of the inheritance (except in the matter of the 

 break-down of salmon into all the shades from very pale salmon to 

 strong golden yellow) and the adherence or approximation to Men- 

 delian numerical proportions are striking. But these two features have 

 also their marked exceptions in other series of crossings. 



In mating Bagdad white cocoon race with Japanese green cocoon 

 race white, greenish white, green, greenish yellow and yellow cocoons 

 are got in the first generation. 



In mating Bagdad white cocoon race with Persian lemon yellow 

 cocoon race, green and strong yellow cocoons are got in the first 

 generation. In mating Italian Salmon, pale pinkish yellow or salmon 

 cocoon race, with Istrian, strong golden yellow cocoon race, cocoons 

 of all gradations from salmon to golden are got in the first generation, 

 and also in the second generation whatever two cocoon shades be 

 mated together. In mating Italian Salmon and Chinese White, in first, 

 and especially in later generations, there is a strong tendency for all 

 sharp distinction between white and salmon to break down and cocoons 



