20 



SCIENCE 



[N. S. Vol. XXXIV. No. 862 



one of the other race, as in the crosses with 

 Istrian yellow. 



In one case the French yellow mother pro- 

 duced only yellow offspring. This was evi- 

 dently due to complete dominance of yellow 

 in the cross, for white descendants were ob- 

 tained both in F, and in F,. In the two other 

 broods produced by French yellow mothers, 

 both white and yellow individuals occurred in 

 Fj, so that dominance here alternated be- 

 tween yellow and white. 



The reciprocal cross (Bagdad female X 

 French yellow male, Table V.) gave a similar 

 result. In one case, white was completely 

 dominant; in the other two, mixed broods 

 were obtained. 



TABLE v. RESULTS OP MATING BAGDAI> WHITE 



TEMALES DOUBLY, VIZ., WITH BAGDAD WHITE 



AND WITH PKENCH YELLOW MALES 



Fj yellows from a French yellow mother 

 were mated inter se in seven cases. One of 

 the seven pairs produced only yellow F, off- 

 spring, 59 in number, and a pair of these 

 gave, in F,, 47 offspring all yellow, which re- 

 sult indicates that one or both of the Fj yel- 



lows in this case were pure, being derived 

 from a fertilization by sperm of the French 

 yellow male. The remaining six pairs of F^ 

 yellows produced mixed F„ broods aggregating 

 28 white : 107 yellow, or Iw : 3.8y, a small 

 excess of yellows. Four matings of F^ yellows 

 with whites (Table IV., summary) produced 

 mixed broods, aggregating 64 whites : 62 yel- 

 lows, or Iw : ly, as in similar matings 

 (single or double) of Bagdad with Istrian 

 yellow. Two matings of Fj (dominant) 

 whites from a French yellow mother (Table 

 IV.) produced 50 whites : 20 yellows, where 

 3w : ly are expected. In the reciprocal cross 

 (Table V.) Fj whites produced in two cases 

 white offspring only and in a third case aU 

 white but one individual, a possible straggler, 

 while two other pairs gave mixed F, broods. 

 In case of the two F^ pairs which produced 

 only white F„ offspring, it is evident that only 

 one of the white parents can have been pure 

 (derived from a white X vehite fertilization), 

 for yellows were obtained in Fj in three of 

 the four matings made. Matings of F^ whites 

 with Fj yellows were made in three cases, two 

 of which produced mixed broods of approxi- 

 mately Iw : ly ; in the third mating the white 

 was apparently pure (from a white X white 

 fertilization), for the 22 Fj offspring were all 

 white, as were also the " few " Fj offspring 

 descended from them. 



So far there is encountered nothing at 

 variance with Mendelian expectation. But 

 among the F3 broods derived from this cross 

 (Table V.) occur some minor irregularities. 

 However, the numbers in these broods are in 

 general very small, so that this part of the 

 series can not be regarded as very satisfactory. 

 The chief irregularity occurs among the F, 

 progeny of a cross which had given whites 

 only in F^ and lllw : 44y in Fj, a consistent 

 behavior of white as dominant. A pair of the 

 F, whites produced an all white F. brood, also 

 a consistent result, but two pairs of the F, 

 yellows produced mixed F3 broods, viz., 

 17w : 69y where we should have expected only 

 yellow progeny in accordance with the reces- 

 sive behavior of yellow in the two previous 

 generations. (Compare the reciprocal cross. 



