470 ME. H. LTSTEE JAMESON ON 



series are as mucli ligliter than any of the above subspecies as 

 are the latter than the type ! 



Then it was suggested to me that, as in certain districts in 

 the Eastern counties of Ireland a buff- coloured hare {Lepus 

 variabilis) occurs, these mice might be a parallel case. In the 

 first place, I have never seen a bufF-coloured mouse from the 

 mainland of Ireland, and, in the second j)lace, the variation 

 in the hares is apparently a " sporadic sport." Mr. "Williams, 

 the Dublin taxidermist, tells me that he has ta.kea typical 

 leverets and buff ones from the same uterus in bares sent to 

 him for preservation. I have never seen any intergradation 

 between the two colours in the hare. And even if the ultimate 

 cause of the pale coloration in the mice was traced to the same 

 circumstances (whatever they are) which cause the variation in 

 the hare, we have still the fact before us, attested by a comparison 

 of specimens from the mainland with those from the North Bull, 

 that the mean colour of the North Bull specimens is infinitely 

 paler than the mean on the mainland. 



I think, however, that the very great variability of this new 

 race is the strongest evidence of its being a recently evolved 

 variety of Mus musculus typicus, which has not yet settled down 

 into the comparative stability which usually characterizes a 

 species. 



"When I came to enquire into the probable age of this colony, 

 I was confronted with some very remarkable topographical 

 evidence. Being convinced that these sandhills had a very 

 recent origin, I referred to such old maps and charts of the 

 Dublin Coast and County as were contained in the National 

 Library of Ireland, and I owe a debt of gratitude to Mr. J. De 

 W. Hinch for the valuable assistance he gave me in hunting up 

 these records. A detailed account of the topography, past and 

 present, of the North shore of Dublin Bay would be out of 

 place here ; and as my friend Mr. E. Lloyd Praeger is at present 

 collecting evidence on this subject, with a view to investigating 

 the origin of the flora of the North Bull, I will content myself 

 with giving such facts as point to the date at which the island 

 first appeared. 



I regret that I cannot give the exact dimensions of the North 

 Bull, it has increased considerably since the last edition of the 

 Six-inch scale Ordnance map was published (1867). Mr. Praeger 



