PROTECTIVE COLORATION IN' THE HOUSE-MOUSE. 465 



On a probable Case of Protective Coloration in the House- 

 Mouse {Mus musGuliis, Linn.), By H. Ltster Jamesok, 

 B.A. (From the Biological Laboratory, E. College of 

 Science, London.) * 



[Eead 2nd December, 1897.] 



(Plate 30.) 



The colony of Mice I am about to describe was found by me 

 in October 1895, inhabiting the sandhills on the North Bull, 

 Dublin Bay. 



This tract of sandhills runs along the coast for about three 

 miles, from Clontarf to Sutton, on the north side of Dublin Bay. 

 A tidal channel of considerable breadth, averaging, I should say, 

 about a quarter of a mile across, separates the sandhills from 

 the mainland at high water, giving place to extensive mud-flats 

 at low tide. A narrow strip of water about 20 yards wide, 

 however, always intervenes, fed by a couple of small streams on 

 the Dollymount shore. A bridge has been built connecting the 

 west end of the island with the mainland, and here also is the 

 North Bull wall, a breakwater running out across the mouth of 

 the Liffey for about a mile, built in 1823. A coastguard station, 

 a cottage, and a golf club-house are the only buildings on the 

 island. 



On the 6th of October, 1895, when walking on the sandhills, 

 I observed some mice running about that harmonized strikingly 

 in colour with the sand, appearing to be of an unusually pale 

 tint. I had the good fortune to capture one of these, and 

 found it to be a pale example of Mus musculus, Linn. En- 

 couraged by this discovery, during the followiug week and on 

 various subsequent occasions as opportunity allowed, I set 

 "Cyclone" traps and was rewarded by obtaining thirty-six 

 specimens, a very large proportion of which were considerably 

 paler than the typical Mus musculus as it occurs in houses and 

 farmyards in Ireland and England. These specimens, as might 

 be expected, varied somewhat in shade of fur among themselves, 

 and my series shows every gradation from the typical Mus 

 musculus to the individual which I have numbered 30 in the 

 following list and in my collection, that being the most extreme 

 case of pale coloration. Striking as is the ligl)t colour of the 

 dorsal surface in this race, it is still more unlike Mus musculus 

 typicus in the ventral fur, which in the majority of cases is pale 

 * Communicated bj Prof. G. B. Howes, Sec. Linn. Soc. 



