652 MIL J. LEWIS BUNUOTK ON TllK [-'^Pl'- ^'^ 



some 500 rats in all were carefully examined antl nieasnred in the 

 flesh. 



Before detailing the results of this examination it may })erha.ps 

 be as well to review roughly the status and problems con- 

 cerning this species, which is best known in tliis country as the 

 " Old English Black Rat." Jlus ratlas is by far the commonest 

 " ship-nit " and has thus become jn'actically cosmopolitan in its 

 distribution, but when it comes in contact with Mas iiorvegicKS*, 

 our common rat, a larger, stronger and more pugnacious species, 

 it has to give way, and owing to this fact it is now extremely 

 scarce in England. 



In the East (India and the Malay States) Mus rattus is still 

 holding its own, although in those localities M. norvegicus is 

 gradually increasing, and in Egypt, while still very abundant and 

 in some places the only house-rat, it is slowly but surely being 

 superseded by the larger and stronger species. 



The ready variability of Mihs ratlas together with the continual 

 crossing of difierent forms due to the importation of foreign 

 varieties on ships, has given rise to such a mass of vai-iation, that 

 the work of the systematist has been rendered veiy diflicult. 



The actual localities from which my specimens came wei-e Ath, 

 Damanhour, Abu Homos, (liza, Fayiim, Foueh, and Cairo. In 

 all except the last two both 21. rait as and M. norvegicus were 

 found in about equal numbers ; at Foueh, however, out of 80 

 rats only three were M. norvegicus. From Cairo itself I did not 

 see many rats, but all those met with were M. rattus ; and Capt. 

 Flower tells me that M. norvegicus is not yet known there. As 

 regards the Giza Gardens, which lie on the opposite side of the 

 river to Cairo, the latter species has only appeared Avithin the last 

 eight years and forms now about 80 per cent, of the rata there. 

 It has entirely ousted the field-rat (.(rr/crt»i/i/s) which used to 

 abound in the Gardens. 



As regards the proportions of the sexes, both 21. norvegicus and 

 the two foi'uis of M. rattus show a slight excess of females, the 

 actual figures being as follows : — 



Percenta,ge of males in M. norvegicus 42 °/„ 



„ „ ]\f. r. tectoram ' 44 "/„ 



,, ,, j\[. r. alexa-uclrinus 50 °/o- 



The higher percentage of females in .1/. norvegicus, if always 

 jiresent, would tend, apart from other reasons, to cause a higher 

 rate of increase of tliis species at the expense of other species. 



In 1)otli species there is practically no difierence in the size of 

 tlK' sexes, but the males have a wider range of variation. 

 Thus we have in 



M. norvegicus J's, hind foot 28 48 nun., ^ '« '^0-44 mm. 

 M. rattus d 's, „ 2(5 88 nun., 9 's 29-88 mm. 



* 3/iw nofi'pc/iriis Erxl. antcdiiti's Mnx (hcuiiniUKs I'all. liy wliich this spccios is 

 bettor known. 



