HEREDITY IN PLANTS, ANIMALS, AND MAN. ole 
At this stage of the investigation a very interesting question arose. 
What would be the result of crossing the ‘‘ no-whites ” with albinos, and 
mating together their offspring ? 
We may represent the factor for white pigment by W, and its absence 
by w. These two factors behave as an alternative pair, according to 
Mendel’s law. The constitutions of the black and the red “ no-whites ” 
wCB 1 wCR 
weB *" wR 
If we eross these with albinos and work out the theory, as in the case 
of the peas, we find that in the first generation we get all normal-eyed off- 
spring, the “ no-whites ” provide the colour factor, the albimos provide 
the white. 
The result of such a cross obtained in an actual experiment is shown in 
the Diagram 9 (the second brood shown on the diagram). The young are 
all normal-eyed blacks. They, however, differ in constitution from any 
black-eyed animals previously obtained, for they carry not only the 
factors for black and red but also the factors for both “albino ” and 
“no-white,’ and are capable of transmitting all four factors to their 
will then be 
children. 
When these animals are mated together, according to the theory, 
which we can work out in the usual way, there should be, out of every 
64 offspring, 48 with white pigment present, and 16 with no white 
pigment. Of these 16 with no white pigment 4 should be AaLso 
ALBINO, that is to say they should, according to the theory, show 
neither white, nor black, nor red pigment. The eyes should be quite 
colourless. 
Animals with quite colourless eyes we had never seen when the theory 
for this cross was first worked out. Would they be produced when an 
actual experiment was made? A pair of these black-eyed hybrids was 
mated. The first brood hatched was a small one, but our pleasure was 
naturally great when we found that it consisted of 2 with normal black 
eyes, | black with no white, and 2 quite colourless, with no eye-pigment 
visible at all. Since then other broods have been obtained, and there is 
no doubt that the facts agree with the theoretical analysis. 
Looked at from a general point of view the cross of the ‘“‘ no-white ” 
with the albino-eye is of great interest, and is particularly instructive. 
We here took the two most degenerate and abnormal types of eye that 
were known, and mated together the animals which carried them. In 
the first generation the offspring have all perfectly normal characters 
and are indistinguishable, as far as their own visible structures are con- 
cerned, from the perfect wild creatures. The factors lacking in one parent 
were supplied by the other parent and perfect children resulted. The 
