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SCIENCE 



[N. S. Vol. XXXIII. No. 855 



and 34 yellow cocoons. Another mating (1908) 

 of a yellow cocooner and a white cocooner from 

 the original F^ lot produced (1909) 20 white 

 cocoons and 19 yellow cocoons. Mating (1909) 

 two of these white cocooners produced (1910) 

 70 white cocoons and no yellow ones, while 

 mating (1909) two of these F^ yellow cocoons 

 produced (1910) 6 white cocoons and 9 yellow 

 cocoons. 



In 1907 a Bagdad White female was mated 

 with a male Istrian yellow from 9 :40 a.m. to 

 10 :45 A.M. and then with a male Bagdad White 

 till death of the moths. This mating produced 



(1908) 29 yellow cocoons. Mating (1908) two 

 of these yellow cocooners produced (1909) 25 

 yellow cocoons and 8 white cocoons. Mating 



(1909) two of these F, whites produced 



(1910) a small all white lot. Mating (1908) 

 another pair of the Fj yellow cocooners pro- 

 duced (1909) 6 white cocoons and 12 yellow 

 cocoons. Mating (1909) two of these F^ white 

 cocooners produced (1910) an all white lot. 

 Mating (1909) two of the yellow cocoons pro- 

 duced 9 yellow cocoons and 6 white cocoons. 

 Mating (1908) another pair of the F^ yellow 

 cocooners produced (1910) 30 yellow cocoons 

 and 9 white cocoons. Mating (1909) two of 

 these yellow cocooners produced (1910) an all 

 yellow lot. Mating (1908) still another pair 

 of the Fj yellow cocooners produced (1909) 19 

 yellow cocoons and 4 white cocoons. Mating 

 (1909) two of these F^ yellow cocooners pro- 

 duced (1910) 29 yellow cocoons and 5 white 

 cocoons. 



These are the records. Their interpretation 

 may be made by any one interested. In 

 scrutinizing them for significance this should 

 be remembered. In ordinary (single) matings 

 of Bagdad White with Bagdad White only 

 white cocoons are produced in F^ and all fol- 

 lowing generations. In mating French Tel- 

 low with French Yellow or Istrian Yellow 

 with Istrian Yellow only yellow cocoons are 

 produced in F^ and all following generations. 

 In mating Bagdad White with Istrian Yel- 

 low usually all the cocoons of the F^ generation 

 are yellow. Mating these together usually 

 produces in F^ generations 3 yellow to 1 white, 

 the Mendelian behavior. In mating Bagdad 



White with French Yellow the dominance of 

 yellow is not so steadfast. There is, as I have 

 shown and particularly emphasized in my 

 1908 paper, more or less aberration from the 

 Mendelian rules in this mating. And indeed, 

 these aberrations are likely to occur in any 

 other crossing of silkworm races. The usual 

 inheritance behavior of silkworm cocoon char- 

 acters is, however, Mendelian. The aberra- 

 tions constitute what I have called " strain 

 and individual idiosyncrasies." This simply 

 means that I believe that there is more in the 

 order of inheritance than is covered by Men- 

 delism. The Mendelian elements in this 

 order are becoming recognizable and familiar. 

 The other elements are not yet so obvious 

 to us. 



In these double matings the aberrations are 

 abundant and conspicuous. After a double 

 mating the whites of the F^ generation mated 

 with other whites of the same generation do 

 not always produce whites. They may pro- 

 duce both yellows and whites. Or this latent 

 carrying of the yellow character by these pre- 

 sumably strictly recessive (white) carriers 

 may not be manifest till an F^ generation. 

 What does this mean? 



In seeking an answer, the state of affairs as 

 regards actual fertilization in these double 

 mating cases must be kept in mind. 



The female receives during an hour's or two 

 hours' coupling a large number of fertilizing 

 cells from a male of her own race (and hence 

 her own cocoon characters). She then re- 

 ceives during another hour's or two hours' 

 coupling a presumably equal number of germ 

 cells from another male of different race (and 

 different cocoon characters). These two lots 

 of active spermatozoa are held in the sper- 

 matheca. Is one group above or in front of 

 the other, so that when an egg arrives opposite 

 the opening of the spermatheca it will neces- 

 sarily be fertilized by one of this upper or 

 front group (the group provided by the second 

 male) ? Or do the actively motile spermatozoa 

 become thoroughly mingled in their fluid ve- 

 hicle so that access to the egg will be accord- 

 ing to the law of probabilities? More likely 

 the latter alternative should prevail. 



