CHAPTER VII 



THE next case to be described is of a somewhat different 

 order. The groups mentioned hitherto are numerically 

 small and differ from the normal multitude in one or a 

 few obvious characters. But in the case to be described 

 now, we cannot speak with decision about a normal 

 multitude and an abnormal group which is among it. 

 When we find, within a limited area, a number of animals, 

 some of which have a certain characteristic while others 

 have not that characteristic, we may divide them into two 

 groups, but we cannot say that the one group is normal 

 and the other abnormal, when the numbers of each kind 

 present in the area are about equal. The rats of Nainital 

 were found to be in this condition. 



Nainital is a small town, lying at an altitude of about 

 five thousand feet among the hills on the southern flank of 

 the great Himalayan range. The compact portion of the 

 town occupies a small area, but the outlying houses are 

 scattered at a distance from one another, so that the 

 cantonment as a whole covers an area of about a square 

 mile. The town is isolated in position, since although it is 

 within thirty miles of the plains yet it is not on the way 

 to any other places. It lies wholly within a crater-like 

 depression, at the bottom of which is a lake. The summits 

 of the surrounding hills stand at about a thousand feet 

 above this lake. The compact portions of the town lie 



