i6 



Memoirs of the Indian Museum. 



[Vol. I, 



Table showing gradation of cranial measurements in different sizes (i.e., ages) of Mus 



rattus. 



Tvengtb of head and body. 



13—15 cm. 

 15 — 16 cm. 

 16—17 cm. 

 17—18 cm. 

 18—19 cm. 

 19—20 cm. 



Total 





<v 

 u 



a 



10 

 8 



f 8 



11 

 4 

 5 



46 



Ö 



^ 



S 'S 



".§ 

 bß c 



> -^ 



Percentage of total length of skull. 



3797 



38-9 



4093 



41-5 



43-87 



45-25 



00 



35- 1 

 340 

 35-4 

 35-7 

 36-7 

 37-5 



13 

 01 



a 



40-4 

 395 

 38-6 

 37-4 

 36-6 

 35-5 





150 

 .14-4 

 13-7 

 13-9 

 141 

 14-2 



o 



Ö0 2 



h4 



11-5 

 11-7 

 12-2 

 12-4 

 12-5 

 12-59 



26-3 

 26-6 

 271 

 27-5 

 27-6 

 28-8 



01 



,0 01 



j! Co 

 M) O 



18-0 

 17-8 

 16-8 

 171 

 16-6 

 16-2 



These tables of measurements establish beyond a doubt that age and size are 

 the only factors in the grouping of the different series, and that the existence of two 

 constant races is impossible. The variation in size is very considerable, for many 

 of the smallest rats, only 14-15 cm. in length, were already mature, to judge from the 

 development of the testes, though still young as shown by the teeth. On two occa- 

 sions I have found rats of this size pregnant. 



Colour. — The very wide range of colour is most striking, and at first most strongly 

 suggested that I must be dealing with at least two species, but further investigation 

 soon showed that every colour may be found in every size of rat, and that very diver- 

 gent colours are linked together by intermediate examples. This is not by any means 

 the only instance in the genus Mus of a great range of colour being noted. Swinhoe in 

 his description of Mus coninga gives no less than five colour varieties " so linked 

 together by intermediate forms that there is no drawing a line between them." 

 Other members of the subfamily Murinae which show the same great range of 

 colour, are Crateromys and Phlœomys ; Crateromys schadenbergi , the beautiful squirrel- 

 like rat of the mountains of Luzon, is found black, grey and piebald ; Phlœomys cumingi 

 is almost as variable as the guinea pig and no less than seven types have been figured, 

 exemplifying every degree of skewbald and piebald coloration.^ Whereas in Bombay 

 the black type of M rattus is the most common, i.e., 30 per cent., here in Calcutta it 

 is so rare that I have only got eight specimens in all, half of which have been specially 

 sent to me from other districts. 



Of the variations of M. rattus as found in Bombay, Liston writes as follows : — 



" Colour, in Indian species, usually brown, more or less rufous or occasionally 

 yellowish-brown ; more rarely blackish-brown or black ; below generally white, 



Abh. fiber Zool. Mus. Dresden, 1896-97. 



