Miscellanea 
245 
1. 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 measurable 
feature at a time. I use the word feature here because an attribute of an organism which 
can be measured is not necessarily a character in the Mendelian sense although it may be in 
certain cases, as for example in the case of total size. If then I am right in supposing that an 
individual cannot rej^resent that notion which we call the type of a race, the idea that type 
individuals are more fertile than their fellows is erroneous. 
2. Two questions have been raised in this discussion. (A) Are type rats the most fertile 1 
(B) Are heavy rats the most fertile ? The subject of fertility is of special interest ; I hope 
therefore that I may be permitted to raise a third question which has a direct connection with 
the subject and with my own observations. 
Professor Pearson inclines to the opinion that fertility is never inherited. He speaks of 
" The absence of inheritance in the case of fertility which seems to be a necessary foundation of 
the idea of Darwinian evolution." This conclusion is based upon observations which have 
shown that in mankind, mice, swine and hens, fertility was not being inherited at the time of 
investigation. I may mention that the same results may be obtained from the silk-moth Attoxtis 
ricini, if all the eggs of a 200 egg mother and of a 300 egg mother be raised, — both mothers 
being selected from the same brood — there will be no appreciable difference in the fertility of 
their offspring as measured by the number of their eggs. But these cases do not prove that 
differences of fertility are not inherited in any case. 
The fertility of a race may be measured by the average number of offspring produced by the 
mothers during their lifetime, although of course it is usually impossible to measure it in this 
manner. As estimated in this way, fertility varies among the many species from less than ten 
to many millions. I cannot understand how these differences of fertility have become established 
if, as Professor Pearson supposes, fertility is never inherited. It may be that there is some 
simple flaw in my reasoning but I have sought in vain for it. No one doubts that the 
differences of form which are characteristic of the various species have been attained through the 
inheritance of variations, i.e. appreciable differences between parent and offspring, and yet we 
are asked to believe that the various degrees of fertility, which are just as characteristic, have 
been attained in some other way, unimagined at present. 
Since I cannot understand how specific differences can come into being otherwise than 
through the inheritance of variations, I conclude that fertility must be inherited on certain 
occasions. Hence, a demonstration such as that made by Raymond Pearl that in a certain 
case fertility is not inherited is to me a clear demonstration of the fact that variation is of two 
kinds, inheritable and uninheritable, i.e. mutation and fluctuation. 
Let me illustrate this question by a particular case. There are in India two kinds of field 
rats known by the generic names Gunomys and Nesokia. Without referring to the many ways 
in which these two genera resemble one another, it may be said that they differ from one 
another in two respects. Gunomys produces larger litters than Nesokia, on the average in the 
proportion of 8:4. Nesokia has larger teeth than Gunomys. These facts are well known and 
may be verified from specimens deposited in the larger Museums. 
The female Gunomys is equipped for the nourishment of a large family, along either side she 
has a continuous row of teats which extend from breast to groin. The Nesokia has teats on the 
breast and in the groin but not a continuous series along the sides. Gunomys extends 
throughout India and beyond its limits. Nesokia is confined to the north-western parts of the 
peninsula. In certain parts of the Punjab, as for example in the Amritzar district, the two 
genera live side by side in the same fields, though not of course in the same burrows. The fact 
that each kind has received a generic name of its own has enhanced the difference between them. 
