Oll the varying dinüiiance of certain white breeds of the silk- worm, etc. 285 



The results of the two former matings were in exceedingly good 

 accordance with those expected by us, except all yellow F3 broods 

 (those marked with an asterisk in the above chemas) in the first 

 mating where we should have expected i w : 3 Y progeny. The result 

 of the third mating was also not expected in our calculation. It is 

 probably due, I think, to the ineffectual copulation of white male. 

 In silk-worm breeding, we often meet with cases where some female 

 moths after having copulated for due time with a healthy male lay 

 eggs all unfertilized. We call it "ineffectual copulation". In the 

 case of a recessive double mating, if such happened, the result would 

 be a normal monohybrid as above quoted. 



C. Posterity of Fj mixed broods derived from heterozygous white 

 fermales doubly mated with white and yellow males. 



Finally a mention should be made of the results of Bagdad white 

 females doubly mated with Bagdad white and French yellow males. 

 Kellogg obtained, as we expected, two sorts of Fi broods, one all 

 white which has already been referred to, and the other a mixture 

 of white and yellow, the behaviour of which in inheritance is tabu- 

 lated pag. 286. 



At a first glance, the results greatly resemble those of the 

 recessive white female matings, but there are some important 

 differences from them, that is to say, the presence of i w : i Y brood 

 in the F2 white series in the former mating and all white F2 in 

 the cross, Fj white x Fi yellow in the latter mating. The}' are 

 never expected in the recessive white female mating. If females 

 were heterozygous white (Ww), however, they should produce i w : i Y 

 or all white broods in F2, since the F^ white consists of, as before 

 stated, WW, Ww, ww and wy and is able to produce ten kinds of 

 broods in Fj. 



As to the minor irregularities found all through his experiments, 

 such as the absence of some expected forms in the few cases before 

 referred to or inconsistent proportions of white and yeUow in some 

 matings, we are rather inclined to believe that some may be due to 

 accident and some to the small number of matings and the worms 

 reared by him, especially in F3 where many forms are expected to 

 occur. 



On the whole, we are, I believe, justified in concluding that the 

 chief causes of so called inconsistent phenomena with Mendelian prin- 

 ciples, such as Kellogg's strain or individual idiosyncrasies or pertur- 



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