I!. !■:. I.LdVD. VAIIIATIUX AMONP, ÏIIK MATS (IF INHIA. :<\:< 



tance of many yanls. Sonie luindreds ol" Uio common kind \vere being laken 

 daily IVom ail parts of the city. As ref>ards colour tho group was a pure line : 

 as in al! melanic rats, the under l'iir and the fur covering the ventral surface 

 was bluish-grey in colour, but liiere was no lra<H' of brown or yellow in anyone 

 of them. 



Certain points must be mentioned in conneclion \\illi tliis rase, in ortlcr to 

 bring oui its full interest. Melanism is very rare in Gunumi/fi. Black rais of 

 tiiis species bave nol Ijeen noiiced outside Rangoon, allhough very large nuni- 

 bers of the common broM n kind hâve heen captured in other parts of Burmah 

 and in India, cspecially in Calcutta and in Dacca. How far they are rare in 

 Rangoon may be judged from the following fact. Afler Ihe capture of the ton, 

 Ihe cotleclors were requesled to look ont for others like them, but il was not 

 until six inonlhs later Ihat [\\o more were oblained, although meanwhile about 

 five lumdred of the normal kind were being caught every day. Thèse two extra 

 ones belonged, most probably. to the same family gronp to whic-h belonged Ihe 

 ten first captured, for they vi^ere found in the same neighbourhood and they had 

 the same peculiar type of skiill, an important fact which will lie described later 

 on. 



The melanic variely of Gunomyx benyalensis [■■> llicrel'ore rare : it is impor- 

 tant to keep Ihis in mind when we consider the question of the origin of the 

 group. Similar groups of the melanic variely ot Mus inttu» are met with occa- 

 sionally especially in sea-port towns. but it is difficult lo form an opinion as to 

 their origin, since this variely occnrs in manyparts of the world and is particu 

 larly common on ships. 



Gunojtii/>< on the other hand is a burrowing rat not fourni on ships and the 

 melanic variety is very rare. It is therefore almost certain thaï the group arose 

 where il was found and it cannot hâve arisen through the élimination of inter- 

 mediate forms, occuring in and around two particular houses of a large town. 



Anolher point which must be noticed is the numerical size of the group, it 

 must hâve contained more than the ten which were captured. Rats breed 

 throughoul the year, therefore since those captured were mature or nearly so 

 we may l»e sure that there were a considérable number of sueklings and half, 

 grown adolescents in the background which were not captured, we may besure 

 that the whole gioup contained at leasl thirty individuals at the time of the 

 investigation. It is certain thaï the whole group possessed the character of 

 melanism and it is almost certain that they possessed other peculiar characters 

 in common. For example, in the five skulls taken from the group which t re 

 available for measurement. the length of the nasal bones expressed as a percen- 

 tage of the total length of Iheskull is belween ôl and '>2 whereasin fifty skulls 

 of the common hrov. n (iimoinys b^ngalenniti taken haphazard from various parts 

 of a large town. this value varies from 28.2 to 51.8, the theorelical mean being 

 rather less than ."(l, besides this the skulls of the melanic individuals are ail of 

 them longer and narrower than usual. The skull of a memlier of the melanic 

 group is seen in fig. '>. A more normal type is seen in fig. i. 



We may be sure that Ihere is no corrélation between melanism and skull 

 form in Gunoini/f:, no such corrélation occurs in any of the other Mitridae, and 

 brown furred spécimens of G. benç/ali'nsis may be Ibund which bave the same 

 unusual type of skull as thèse melanic individuals. Hence the two characters 

 may occur scparately or Ihey may occur logclhcr. Ilicy are nol cunipelled lo 



