150 Experimental Zoology 



white cocoons, are crossed, the offspring (F^ produce only yel- 

 low cocoons. When these hybrids are inbred they give two 

 kind of individuals ; namely, those producing white and those 

 producing yellow cocoons in the proportion of 25.03 per cent 

 whites to 74.96 per cent yellows. The whites are extracted re- 

 cessives, and are found to breed true. The yellows are of two 

 kinds, one kind giving only yellow-producing offspring (the ex- 

 tracted dominants) and the other kind producing yellow as well 

 as white in the proportion of 3 to i (the dominant reces- 

 sives). A more complex result was obtained when Japanese 

 "whites" and Siamese "yellows" or when Japanese "whites" 

 and European "yellows" are paired. The first generation give 

 offspring that produce yellow cocoons. When these indi- 

 viduals are paired, they give in the second generation four 

 kinds of cocoons: (i) pure yellow, 70 cases; (2) pale pinkish 

 yellow, 2 1 cases ; (3) greenish white, 24 cases ; and (4) pure 

 white, 12 cases. 



The results show apparently that we have to do here with three 

 characters, one of the races used being a monohybrid and the 

 other a dihybrid. In subsequent generations the pure white 

 type breeds true. Some of the yellows give only yellows ; others 

 give white (25 per cent) and yellow (75 per cent); others give 

 yellow (75 per cent), flesh-colored (25 per cent), and still others 

 white and greenish white (25 per cent), yellow (56 per cent), and 

 flesh-colored (19 per cent). 



The flesh-colored forms of the second generation gave white 

 (25 per cent) and flesh-colored (75 per cent). The greenish 

 white type of the same generation gave white and greenish white 

 offspring. 



Toyama used two breeds of caterpillars, pale whites character- 

 ized by the absence of markings, and striped whites having dark 

 stripes. The former breeds true, while the latter produces some 

 pale whites and is therefore a cross breed form. The hybrids 

 produced by uniting these breeds were white and striped worms 

 in equal numbers. In subsequent generations the whites re- 

 mained true while the striped kind gave both whites and striped. 



