278 E. J. ALLEN AND E. W. SEXTON. 
Cross B. 
CROSS BETWEEN THE ALBINO FEMALE AC, AND BLACK HYBRID MALE K.A. 
(i.e. a black carrying red). (Plates I and IL.) 
The albino female that was used in Cross A was also crossed with a 
black hybrid male, the son of a pure black father by a pure red mother. 
The result was 7 black and 2 red offspring in the first brood. 
If the constitution of the albino female is : : and of the hybrid black 
male as , the result of the cross should be 3 blacks (one pure and two 
hybrid) and 1 red, all of them carrying the factor for albino. 
Three further broods were obtained from this cross, the total numbers 
for all four broods being 75 black, 15 red, a proportion 5 : 1 instead of 
3:1, but three of the broods were not counted until some days after 
extrusion, which probably accounts for the small proportion of reds. 
F.1. GENERATION. BLACKS. 
Of the 75 black-eyed young, 49 reached sexual maturity, 27 being 
males and 22 females. Of these it was possible to test 33 from Broods 
II, 111 and IV by mating them together or with mates of known con- 
stitution, and 21 proved to be hybrids, i.e. carried both the factors B and 
R, whilst 12 were pure black. All without exception had albinos amongst 
their immediate offspring, or transmitted the character to their descen- 
dants, showing that both parents possessed the factor c. (Plate I: 
Broods1l, Ll, LV;: V.) 
The following list gives the constitution of each individual animal 
and the different matings made to prove that constitution ; these constitu- 
tions are shown in detail on Plates I and IT. 
If.A. Male, Black carrying Red and Albino (Plate IT). 
Matings :— (1) with female D of the same brood (B+ 4A); 
88 young, 65 Black, 23 Albino ; 
(2) with female VI.A (B+R-+ A); 79 young, 
49 Black, 15 Red, 15 Albino ; 
(3) with a female (B+ R) (from a mating Pure 
Black with Pure Red); 26 young, 18 
Black, 8 Red. 
I].C. Male, Black carrying Red and Albino (Plate II). 
Matings :—(1) with female VI.C. (B+R-+ A) ; 115 young, 
74 Black, 15 Red, 26 Albino ; 
(2) with Red No-white female from No-white 
Stock (previously mated with male 
VI.A.t.) ; 34 young, 18 Black, 16 Red. 
