36 NATURAL HISTORY 



mice which I mentioned to you in town. The person that 

 brought me the last says they are plenty in harvest, at 

 which time I will take care to get more ; and will endeavour 

 to put the matter out of doubt, whether it be a nondescript 

 species or not. 



I suspect much there may be two species of water-rats. 

 Kay says, and Linnaeus after him, that the water-rat is web- 

 footed behind. Now I have discovered a rat on the banks 

 of our little stream that is not web-footed, and yet is an 

 excellent swimmer and diver : it answers exactly to the 

 Mus amphibius of Linnaeus (see Syst. Nat.) , which he says, 

 f{ natat in fossis et urinatur." I should be glad to procure 

 one " plantis palmatis." Linnaeus seems to be in a puzzle 

 about his Mus amphibius, and to doubt whether it differs 

 from his Mus terrestris ; which, if it be, as he allows, the 

 " Mus agrestis capite grandi, brachyuros," of Ray, is widely 

 different from the water-rat, both in size, make, and 

 manner of life. 1 



As to the Falco, which I mentioned in town, I shall take 

 the liberty to send it down to you into Wales; presuming 

 on your candour, that you will excuse me if it should 

 appear as familiar to you as it is strange to me. Though 

 mutilated, qualem dices . . . antehac fuisse y tales cum sint 

 reliquice I " 



1 Willughby was the originator of the confusion alluded to, as 

 pointed out by Mr. Bennett in a note to this passage. He described 

 the water-rat as having its toes connected together by intervening 

 webs ; and his description was published by Ray in the " Synopsis 

 Quadrupedum." Linnaeus, believing that such authorities were to be 

 relied on, admitted into several editions of his " Fauna Suecica " a rat- 

 like animal, having its hinder feet webbed. Subsequently, however, 

 he referred to it as of doubtful existence, as being perhaps inaccurately 

 described, and as probably to be referred to his Mus terrestris. Wil- 

 lughby's error no doubt was occasioned by his having assumed from a 

 certain habit that a certain structure which he regarded as indicated by 

 it must necessarily be coexistent with it. 



The Mus agrestis capite grandi, brachyuros, of Ray, is the short- 

 tailed fi^ldffiouse or vole, Arvicola agrestis, LINN. ; the water rat, or 

 rather water vole, being the Arv. amphibia, DESM. The hybernaculum, 

 1 or winter nest of the water vole, is described later by White in his 

 ~ twenty-sixth letter to Pennant. ED. 



