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. 
Ray says, and Linnaeus after him, that the water-rat is web- 
footed behind. InTow 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, 
" 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.* 
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, tales cum sint 
reliquiae ! 
* 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 doubtftil existence, as being perhaps inaccurately 
described, and as probably to be referred to his Miis 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^ bracht/uros, of Ray, is the short- 
tailed field mouse or vole, Arvicola agrestis, Linn. ; the water rat, or 
rather water vole, being the Arv. amphibia, Desm. The Tiybemmulum, 
or winter nest of the water vole, is described later by White in his 
twenty -sixth letter to Pennant. — Ed. 
