244 THE ZOOLOGIST. 



feel quite sure, judging by habit and disposition, that these two 

 Mice are of separate species. Also by the fact that you never 

 see a specimen where there is a mixture of the two character- 

 istics. I think I may speak with some authority on this subject, 

 as I always keep, and have done so all my life, a number of 

 the small mammals native of Britain." 



Here these interesting notes end, and, I thought, were fairly 

 conclusive until I had a letter from Mr. J. G. Millais. This 

 gentleman, at my request, very kindly read through this paper, 

 and wrote to me as follows : — 



" I agree with you in that jiavicollis is a good species. Mus 

 jiavicollis wintoni is a subspecies. A slightly different island 

 form of the Continental one, and is, I think, our form of Mus 

 Jiavicollis. It is distinctly smaller and less richly coloured* 

 than those of Hungary, Bohemia, &c. 



" The large form of Mus sylvaticus from Shetland is just as 

 large as any wintoni. 



" I am convinced M. wintoni and sylvaticus do not always 

 fight " (here Mr. Millais's experience and my above correspon- 

 dent's differ) " and kill each other, but frequently breed 

 together.! I have plenty of Mus wintoni (i. e. jiavicollis) and 

 sylvaticus and the hybrid here in my garden. I agree with you 

 that what you call jiavicollis, i. e. wintoni, is on the increase, 

 certainly in the southern counties." 



I consider myself most fortunate in having the opinion of 

 so great an authority as Mr. Millais, whose splendid volumes on 

 British mammals must, at any rate for years to come, stand 

 unrivalled. As a help to those who I earnestly wish would 

 try and work out the range of Mas jiavicollis in Britain, I 

 give below a minute and detailed description of an adult and 

 typical jiavicollis, together with its synonymy and average 

 measurements. 



The Yellow-necked Mouse. 



Mus jiavicollis, Melchior, ' Den danske Stats og Norges 

 Pattedyr,' p. 99 (1834) ; Be Winton, ' Zoologist,' 1894, p. 441. 



* I have an example from Gloucestershire which is one of the brightest 

 coloured jiavicollis I have ever seen. 



f Personally I have long suspected this too. 



