July 7, 1911] 



SCIENCE 



17 



TABLE I. RESULTS OP SINGLE MATINGS OP BAGDAD 

 WHITE WITH ISTEIAN YELLOW SILKWORM MOTHS 



In double matings of these same races there 

 is only this difference to be borne in mind; 

 the egg may have been fertilized either by a 

 sperm of the same race or by one of the other 

 race. In the former case we should expect 

 the Fj individuals all to be like the mother, 

 and all to treed true in F^, whereas in case 

 of a cross we should expect F^ sometimes and 

 F, always to consist of a mixed brood. 



Kellogg reports six such double matings 

 (Tables II. and III.), three of which gave all 

 yellow Fj broods (except for a single possible 

 " straggler ") ; one mating gave only white Fj 

 offspring, while two gave both sorts in F,. 

 Seven pairs of Fj whites (from a Bagdad 

 white mother. Table II.) gave only whites in 

 F„ as well as in F,. Clearly the egg of the 

 Bagdad mother was in each of these eases fer- 

 tilized by sperm of the same race. At any 

 rate the behavior through three generations is 

 exactly the same as in the pure Bagdad race 

 and shows no " perturbation " whatever. 



^Erom Fi of last cross in Table I. 



One other mating of F^ whites inter se gave 

 in F,, 46 whites : 15 yellows, or 3w : ly, as 



TABLE II. RESULTS OP MATING BAGDAD WHITE 



FEMALES DOUBLY, VIZ., WITH BAGDAD WHITE 



AND WITH ISTRIAN YELLOW MALES 



we should expect the white F' individuals to 

 do when produced by a single mating between 

 the white and the yellow races used. 



