288 E. J. ALLEN AND E. W. SEXTON. 
‘6 
Of the offspring of the cross between the “ all-white ” perfect-eyed 
male and the albino imperfect-eyed female, three only survived until 
they were mature, 2 black-eyed and 1 red-eyed, all being females. Of 
the F, offspring of the cross between the imperfect albino and the hybrid 
black already dealt with (Cross B) there were four survivors of the first 
brood (II), one black female, one red and two black males, as already 
described. At this stage of the investigation it was important to crease 
as quickly and with as little risk as possible the stock of albino-eyed 
animals. This could be most easily done by crossing the two broods, 
which soon gave us large numbers of albino-eyed offspring. This crossing 
of the two broods has somewhat complicated the analysis necessary for 
the determination of the germinal constitution of the perfect-eyed 
“all-white ” male, but the result nevertheless appears to be definite and 
not without interest. 
The following matings were made, the offspring of Cross C being 
designated VI, those of Crass B being II (Plate IT) :— 
(1) VI.A. (Black female) xII.A. (Black male). The offspring were 
black, red and albino, hence both male and female were hybrids, carrying 
factors for black, red and albino. 
(2) VI.C. (Black female) xJI.C. (Black male). Again the offspring 
were black, red and albino, and both male and female therefore 
hybrids. 
(3) VI.B. (Red female) « I.B. (Red male). Offspring red and albino. 
(1) and (2) bemg quite similar crosses their offspring may be added 
together. In three broods from each, examined immediately the young 
were extruded, there were 91 black, 26 red and 37 albino, a total of 154 
young. 
In the cross of the two reds (3), out of 101 young there were 76 red and 
25 albino. 
We must now proceed to consider the analysis of these matings accord- 
ing to the two hypotheses for the constitution of the perfect-eyed * all- 
white > male already mentioned, in order to determine which, if either, 
of the two hypotheses 1s correct. 
Taking first the cross between the two blacks, we have :— 
Hyporuesis I. On the first hypothesis the constitution of the all- 
white perfect-eyed male will be ~, that of the albino female carrying 
2 
Paul ( 
black and red a The gametes for the male will therefore be C only, 
for the female ¢ B and ec R. The F, zygotes resulting from the mating 
of these two will be Ce B and Ce R, giving black and red-eyed animals 
in equal numbers. 
