^SCIENTJnC JiESULTS FROM THE MAMMAL SURVEY. 65 



mostly pure white or lemon coloured 

 to their bases ; coat soft and usually- 

 thick.. . ... ... ... ... R. rattus frugivorus, 



Raf. 



Specimens intergrading in appearance between these subspecies 

 usually come from colonies of mixed origin, e.g., those of ships or 

 of large towns. Where opportunities ibr pure breeding occur, as 

 on small islands, each of these subspecies breeds perfectly true to 

 type. It is, of course, unfortunate that the typical form of the spe- 

 cies, in a technical sense, is B. r. o'cUtus (which is little better than 

 a domestic animal), and not the really wild form, M. r. frugivorus. 



Turning now to India, the rats listed in the Survey Reports as 

 " rufesceyis " , or " r«yescews var.", afford us with problems of con- 

 siderable complexity. In the first plav^e, although I am unable to 

 find any character in the dentition, skull, or external parts, to 

 distinguish any of them satisfactorily from R. rattus, the range of 

 variation is enormous. Indian skulls with well worn teeth have 

 the condylo-basal length ranging between 34 and 44 mm. The fur 

 may be long, soft, dense and without spines; or it may be short, 

 thin, and harsh, with numerous spiny bristles. 'YA\b dorsal colour 

 varies between bright rufous, or warm olivaceous tints on the one 

 hand, to dull tawny, or cold mixtures of black and grey on the 

 other. The underparts may be pure white or pale lemon ; or they 

 may be slat}', with or without a rusty tinge or bloom. The hands 

 and feet may be white or yellowish above, with or without dusky 

 markings ; or they may be wholly blackish brown in colour. The 

 mammary formula may be 2-3 = 10 or 3-3=12. Every intermediate 

 stage between the extremes indicated may be found in the collec- 

 tions before me. Nevertheless, much of this variation has a 

 definite geographical value ; and where long series are available 

 from one locality or district, the rats are usually lound to conform 

 closely to one or more definite local types. It is therefore possible 

 to define a considerable number of local races or subspecies. 



The members of the rattus group seem to afford an exception to 

 the rule, so general for wild mammals, that not more than one 

 subspecies of a given species, or not more than one of two or more 

 very closely allied species can inhabit a given locality. But these 

 rats are capable of playing many parts in warin countries 5 thus we 

 find them following a free life in fields and hedgerows, far from 

 houses, or high up among the branches of trees in forests ; or they 

 may lead a purely parasitic existence in human habitations or 

 shelters. It is a poor sort of locality which refuses at least two 

 " niches in nature " for rattus ; and the semi-domesticated stocks, at 

 all events, of this species have frequent opportunities for prospect- 

 ing and touring conferred upon them by railways, wheeled 

 carriages, and shipping. 

 9 



