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observations, shown that there was no maximum fertility at all, it is hard to comprehend what 
value he set on his observations. Apparently, he desired to show that a maximum fertility 
could exist not associated with the type character. That I take it would be a new principle, 
and one which I should have said would have an enormous bearing on Evolution. As a matter 
of fact in the " Conclusions " given in his memoir (p. 264), there is no reference to (A), but the 
result (B) he emphasises by italics. 
" There is clear evidence that the largest and smallest rats are quite as fertile as those of 
average size " (p. 264). As there was " clear " evidence of the exact opposite of this statement 
in his observations, and as the age and number of litters of his rats were not given, it was 
quite impossible to determine from Captain Lloyd's data, whether (i) there was any maximum 
fertility at all associated with size and (ii) if there were, with what size it was associated. 
Professor Lloyd drew the very definite conclusion that fertility was not related to weight 
in his rats ; Fraulein Hanel drew the very definite conclusion that there was no inheritance 
within the "pure line" in her Hydra,. Both of these conclusions were erroneous, as the most 
elementary statistical examination would have shown either of them. I used both to illustrate 
the point thrust on me daily by the examination of many memoirs that biology cannot 
safely do without biometry. Professor Lloyd states that some principle enunciated by me is 
"now occupying a prominent position in a well-known text-book." I cannot be responsible 
for that text-book, whichever it may be, nor how the principle may be stated. The essential 
contributions I have made to this supposed principle may be summed up as follows. 
(i) Genetic selection, i.e. fertility correlated with a somatic character will modify natural 
selection, unless the modal somatic character exhibits the maximum fertility. A progressive 
change in type would follow any other association until the modal value became that of 
maximum fertility. (Phil. Trans. Vol. 187, A, 1896, p. 258 ; Vol. 192, A, 1899, p. 258, etc.) 
I cannot see any flaw in this argument whatever. 
(ii) Genetic selection either does not exist or if it does there is instability in the race. 
In the Grammar of Science (2nd Edition, 1900, p. 440 et seq.) I referred to two species of 
flowers in which I had found the modal capsules to contain the greatest bulk of fertile seed. If 
I had found non-modal capsules to contain such bulk of fertile seed, I should, having shewn 
that the character I was dealing with was inherited, have argued that the plant in question 
was changing or could change its type independently of natural selection, i.e. that genetic 
selection would at least modify if it did not overmaster natural selection. If Professor Lloyd 
had been right in asserting that there was no relation between fertility and weight in his rats 
then there could be no genetic selection, and what he calls my principle could not come into 
play. For the basis of that principle lies in the words : " If fertility be correlated with any 
organ or character." Actually Professor Lloyd's data showed a considerable correlation between 
weight and size of litter ; and if this had been correct then genetic selection would have 
come into play and he would have reached an important result— -just the reverse of what he 
himself drew from his own statistics ! — As a matter of fact, I think his material was vitiated 
because he had not inquired into the age factor and the correlation of age and size of litter in 
his rats. There was nothing in his material which would demonstrate or refute the principle 
that when fertility-differentiation exists and is correlated with somatic character, then the 
modal character must be associated with the maximum fertility, or the race will lack stability 
in type, until this association is attained. Professor Lloyd remarks : 
"The conclusion that there is a strong tendency for the character of maximum fertility to become 
one with the character which is the type is in my opinion unjustifiable in any case, because it seems 
that an individual cannot represent the type of its race as regards all its features. We can only speak 
of a typical individual when we are dealing with one measuiable feature at a time." 
