52 SKETCH OF THE HISTORY OF MAMMALIA. 



summit of the island, where the common mouse likewise 

 occurs. It is often seen running- about by day, and was 

 found in numbers when the island was first colonized by 

 the English a few years since. The other and browner 

 coloured variety lives in the outhouses near the sea-beach, 

 and feeds chiefly on the offal of the turtles slaughtered 

 for the daily food of the inhabitants. If the settlement 

 were destroyed, I feel no doubt that this latter variety 

 would be compelled to migrate from the coast. Did it 

 originally descend from the summit? and, in the case 

 first supposed, would it retreat there ? and if so, would 

 its black colour return ? It must, however, be observed 

 that the two localities are separated from each other by 

 a space,' some miles in width, of bare lava and ashes. 

 Does the summit of Ascension, an island so immensely 

 remote from any continent, and the summit itself sur- 

 rounded by a broad fringe of desert volcanic soil, possess 

 a small quadruped peculiar to itself? or more probably, has 

 this new species been brought by some ship from some 

 unknown quarter of the world ? Or, I am again tempted to 

 ask, as I did in the case of the Galapagos rat, has the com- 

 mon English species been changed by its new habitation 

 into a strongly marked variety ? — D." (' Zool. of Voyage 

 of Beagle,' p. 36.) 



This zoological problem is one of the many so difficult 

 to solve. Mr. Waterhouse remarks, '' It appears as if the 

 brown and black rats(ilf. decumanus and M. rattus), and 

 likewise the common mouse, all of which follow man in 

 his peregrinations, and which to a certain degree are 

 dependent upon man, and may therefore be termed semi- 

 domestic animals, are, like really domestic animals, sub- 

 ject to a greater degree of variation than those species 

 which hold themselves aloof from him," (Ibid.) 



The common mouse is undoubtedly indigenous in 

 Europe ; and has been known from the earliest times : 

 it is the Anglo- Saxon Mus, the German Maus, the 

 Danish Muys, the Latin Mus, and the Greek MGs. In 

 Spanish its name is Rat ; in Portuguese, Ratinho ; in 

 Italian it is called Sorice ; and in French, Souris : from 

 the Latin sorex, employed by zoologists to designate 

 the Shrews. 



