138 THE ZOOLOGIST. 



This latter character the following measurements will show : — 



Typical Mils mus cuius. 

 Head and body 84 81 74 mm. 

 Tail ... 82 81 73 mm. 



Wild Form. 

 Head and body 77 77 77 76 78 mm. 

 Tail ... 65 61 62 62 57 mm. 



Nearly a score of the wild form have been trapped, and of 

 these not one has shown the slightest tendency towards inter- 

 gradation with the true Mus mus cuius, while their constancy in 

 colour and proportions has been very noticeable. In fact, no one 

 who had seen them in the flesh could doubt their essential dis- 

 tinctness from that animal. 



This being the case, it is evident that in the Wild Mouse we 

 have to do with a genuine indigenous species, occurring side by 

 side, but not mixing with the introduced form. It is therefore a 

 new addition to the fauna of Portugal, and its non-recognition 

 hitherto has been, of course, due to its resemblance and close 

 relationship to the introduced Mus musculus. Like the Mungoose 

 and the Genet, it forms part of the N. African element in the 

 Portuguese fauna, but whether, like the last-named, it penetrates 

 into S. France, or like the former is confined to the Peninsula, 

 still remains to be determined. Visitors to Pau, Biarritz and 

 other southern places might occupy themselves pleasantly and 

 advantageously by measuring and skinning any mice that could 

 be trapped there in order to clear up this interesting point. 



What the name of this wild form should be must unfortunately 

 remain doubtful for the present. Several such mice have been 

 described from N. Africa, among others Mus spretus, Lataste, and 

 M. algirus, Loche ; while further east similar forms have been 

 called Mus bactrianus, Blyth, and the exact relationships of all 

 these to each other and to the Portuguese animal must be better 

 understood than at present before the proper names for them can 

 be settled. Another mouse of the same group is that discovered 

 on the Salvage Islands by Messrs. Grant and Baring, to which 

 also I have not as yet ventured to assign any definite name. 



All these forms of the Mus musculus group will, it is true, be 

 probably only looked upon as geographical subspecies of the 



