370 Maternal Inheritance and Mendelism 



Back-Grossing. 



(1) (2) 



( ? F[ X i Bombyx) ( ? Bombyx x i F{) 



I I 



Eggs of first back-crossinK T N 



I I 



T 



second „ (T + N + M) 



I 

 third ,, W 



I 



fourth ,, {T + N + M) 



I 

 fifth „ W 



I 

 constant 



We see that the phenomena of inheritance observed in Fi eggs and 

 in back -crosses are exactly maternal, no trace of paternal inHiience, and 

 that both Tlieophila and Bomby.c colonred characteristics segregate from 

 each other, and may be extracted again in their original form. 



Series 2. Crosses between the Whitish grey-egged a)id 

 Normal-egged forms. 



In the spring of 1909, we made crosses between the whitish grey- 

 egged and the normal-egged breeds. The grey-egged breed nsed in this 

 series of experiments was the very same breed used in the second series 

 of experiments before mentioned, that is to say. Grey No. 24. Normal- 

 egged breeds were: (1) tetravoltine white (Onodahime), (2) divoltine 

 albino extracted from a cross between divoltine " Chiyodzuru " and 

 "Chiisu" albino, (S) divoltine " Shinkawachi," and (4) " /T^ albino" 

 extracted from a cross between Japanese tetravoltine white and the 

 wild mulberry silk-worm. 



(a) Tetravoltine normal-egged female.s (Onodahime) mated with 

 males of Grey No. 24. 



Three matiugs were made in the spring of 1909 which gave all 

 normal divoltine white F^ eggs. Of the summer broods derived from 

 the Fi eggs, those from two batches yielded both normal and grey 

 (34 normals and 15 greys) F„ batches and the remainder only normal 

 batches. 



Some of the F^ batches hatched in August, which were the third 

 brood of 1909. Seven batches were reared sepaiately and when 



