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I will now dwell for a moment on their resemblances as they can be seen at Amritzar. I have 
elsewhere related of a certain observer, who although in the habit of handling large numbers of 
each kind daily, yet regarded them as of one race. Probably most people would have made the 
same mistake. The teats are hidden in the fur. The dental difference is not obvious until the 
skull has been extracted and cleaned. Gunomys is on the average larger than Nesokia but their 
ranges of variation overlap in this respect. The fur is very variable, but exactly the same 
varieties of tint and texture are to be found in both genera. In the investigations round 
Amritzar large numbers of the burrows of both kinds were opened up, and it was finally decided 
that there must be two races present because the nests were found to contain either few or 
many young ones. This conclusion was of course fully borne out when the number of the teats 
was noticed. I dwell on these points in order to demonstrate the remarkable resemblance 
between these two genera. This can be illustrated in another way. It is well known that 
among mammals the form of the skull is one of the most definite points for classification. The 
various domestic races even possess their own type of skull in many cases. But if we examine 
the skulls of these two genera we find a remarkable degree of resemblance. When looked at 
from above or from the side the two kinds cannot be distinguished from one another with 
certainty, but from below they can be recognised at a glance. The palatine foramen of Nesokia 
is about half as long as that of Gunomys. The roots of the incisor teeth come to an end on 
either side of the palatine foramen ; in Gunomys they cause a slight narrowing of the posterior 
part of the foramina, but in Nesokia in which all the teeth are larger, they encroach so much 
upon these foramina as to abolish them posteriorly. These points are shown in the diagrams 
which have been traced from photographs. The great resemblance in general form between the 
two skulls on the left is obvious, the skull of a Mus is shown in contrast. 
Except for the small difference in the teeth and palatine foramen, the difference in fertility is 
the only essential point of distinction between the two genera. No one who has examined the 
skulls of these animals will doubt that the two kinds are very closely related genetically. As 
regards the shortness of the palatine foramen, Nesokia stands alone among the different genera 
of the Muridae; this is good reason for supposing that Nesokia was derived from Gunomys, 
a view which is supported by their Geographical distribution. But for the sake of our argu- 
ment it is unnecessary to press this point. Let us suppose that the Gunomys was derived from 
the Nesokia or both from a common stock. In any case how can they have arrived at their 
present condition unless fertility was inherited ? The more I think over this case, the surer 
I feel that differences of fertility must have been inherited. Can Professor Pearson show us the 
way out of the difficulty 1 
3. We do not know how the one genus was derived from the other. No one observed the 
event or events which led to the establishment of the newer genus, but we can do more than 
guess at the manner of them. Our imagination may be guided by certain knowledge of other 
events which have been observed. We know that a pair of guinea-pigs in captivity may give 
rise to a hundred or more healthy looking members of their own kiud in a few years. We also 
Nesokia 
Gunomys 
Mus 
