1909. J R. E. IvLOYD : The Races of Indian Rats. 17 



pads, number of palatal ridges, number of rings on the toes, length 

 of hair on the tail, and its relation to the length of the scales, differ- 

 ence in colour of the hair above and below the tail, the number of 

 teats, relative proportions of the skull. Where possible, these fea- 

 tures were measured, but the measurements will not be recorded 

 here as the}^ show no useful results. Except for the number of 

 palatal ridges, all these points were found to vary within wide or 

 narrow limits. But deviation from the normal in any one character 

 was not regularly associated with deviation in any other character. 

 The group seemed to form one race. That they are one race is 

 shown by the large series of measurements of lengths. The measure- 

 ments, which were recorded in millimetres, were arranged in a series 

 of ascending values. The numbers of rats of each length were 

 added together, so that the whole collection became resolved into 

 a series of groups, all the rats of a particular length forming one 

 group. As the collection contained adult rats the lengths of which 

 were as low as 140 mm., and as high as 225, every intermediate 

 value between these extremes being met with, the number of the 

 groups was large. The number was divided by 5, by contraction 

 upon every 5th group. For example, the numbers of rats measur- 

 ing 153, 154, 156 and 157 mm. were added to the number which mea- 

 sured 155, Those measuring 158, 159, 161 and 162 mm. were added 

 to those measuring 160 mm. The results are shown in a diagram 

 (text- fig. i) in which the horizontal lines show the lengths in an 

 ascending series, from the left, and the vertical lines indicate the 

 numbers of rats of, or closely approximating to, each length. The 

 diagram shows that rats of about 175 mm. form a majority, that this 

 value is approximateh^ the mean length of the race, and that the 

 numbers of rats of each length become fewer as their lengths become 

 further removed from, the mean. It shows, however, that indi- 

 viduals 225 mm. in length can be found and that they are clearl^^ 

 of the same race as those of 180 mm. 



It must be pointed out that in constructing the diagram a large 

 number of immature individuals have been included. Their presence 

 accounts for the wider range below the mean than above it, which the 

 diagram exhibits. It is well known that in any character capable of 

 measurement, a group of related organisms shows equal deviation 

 from the mean, 'both above and below it. We can infer therefore 

 that, since there are at least three individuals of 225 mm. length {i.e., 

 45 mm. greater than the mean), there must be a small number of 

 mature individuals 135 mm. in length or thereabouts, and that the 

 range in the length of the race is not less than 90 mm. Examina- 

 tion of rats of about 140 mm. length shows that some of them 

 have the 3rd molar worn, and this is usually considered a sign of 

 maturity. No doubt can be thrown on the maturity of a certain 

 small specimen — R. S. No. 674 — which measures 140, 155, 28, 

 14 mm., and weighs 65 gms., the 3rd molar being well worn. The 

 specimen has been sent in spirit complete, so as to show that the 

 uterus contains two embr^'os in an advanced stage of develop- 

 ment. 



