248 Recent Advances in the Study of Heredity. 
portion in which the various types of individual will occur will be 
as follows : — 
a. b. c. d. 
Y-R 1 Y-W 1 G-R 1 G-W 1 
(H)Y-R 2 (H)Y-VV 2 G-(H)R 2 
Y-(H)R 2 
(H)Y-(H)R 4 
9 3 3 1 
Each of the numbers in the columns a, b, c, and d in the second 
Table is arrived at by multiplying the figures to the left of the 
two characters, in the first table, which are borne by each zygotic 
type in the second. 
The fact that not only the distribution 9 YR, 3 YW, 3 GR, 
1 GW, but the various zygotic types within 3 of these categories, 
can be deduced from data other than the nature of the contents of 
the gametes concerned in producing this assemblage of forms is of 
no small importance ; because it takes the ground from under the 
feet of any advocate of the Mendelian hypothesis, who might argue 
that it was highly improbable that a theory, which accounted not 
only for the proportion 1 : 2 : 1, but for the complex condition of affairs 
involved in the proportion 9: 3 : 3 : 1 ; and subsequently for the 
proportions 9:3:4 and 9 : 7, could be unsound. Let me express 
what I mean in another way. The Mendelian advocate might argue 
thus: “ It may be that the theory suggested by Mendel is not the true 
explanation of the results it is designed to explain ; and that it is a 
pure fluke that the agreement between hypothesis and experimental 
results is so close. I think this highly improbable, but I am ready 
to admit that this may be so. But surely, if starting with this 
theory, we can go on to explain the proportion 9:3:3: 1 and 
9:3:4, it is inconceivable that the theory from which we started 
is not the true explanation of the 1:2:1 proportion.” The fallacy 
in this argument is that the 9 : 3 : 3 : 1 ratio, although, of course, it 
can be deduced from the 16-square Table, follows merely from the 
3 : 1 ratio ; and, not only so, but the various zygotic types within 
the categories can be deduced from the 1:2:1 ratio. My present 
belief is that Mendel’s theory is very close to, if it is not actually the 
true explanation of the phenomenon of segregation ; but I think it is 
important to realise that the fact that the 9:3:3: 1 ratio, and 
others which follow from this ratio, can be deduced from this 
theory, is no more a proof of its truth than the fact that the 
1:2:1 ratio is consistent with it. 
