DAUBENTON'S BAT. 61 



obligingly permitted the use of his specimen, which 

 is an adult male, and was taken at Milton Park in 

 Northamptonshire : our late revered friend Mr. Yarrell 

 also kindly allowed the use of his specimens, consist- 

 ing of an adult female, a half-grown male, and an 

 extremely young one, all of which were taken at 

 Islington. It was upon an examination of these that 

 the statement respecting their identity with Vesper- 

 tilio Daubentonii was made in the first edition of this 

 work, a decision which has met with universal assent. 

 The expression " oreilles petites," in Desmarest's essen- 

 tial character of V. Daubentonii, is so vague as to be 

 useless, and at the same time conveys an idea which is 

 absolutely erroneous ; and were it not corrected by the 

 statement of the actual length of the ears, namely, 

 half an inch, it would greatly mislead any one who 

 depended upon it. Such uncertain and arbitrary ex- 

 pressions in essential specific characters cannot be too 

 strongly deprecated. In any group of animals in which 

 the distinctive characters are not very obvious, and are 

 frequently dependent upon the comparative dimensions 

 of small or inconspicuous parts, it is of the greatest 

 consequence that the relative proportions be accurately 

 stated ; and if this be done, they form the most certain 

 and valuable marks of distinction. 



So peculiar are the vespertinal habits of this species, 

 that, while very abundant, an ordinary observer might be 

 quite unconscious of its existence. It is essentially an 

 aquatic species, if such an expression be admissible, 

 applied to an animal which never enters the water. It 

 haunts that element continually, flying so near its surface 

 as to render it difficult to distinguish between the creature 

 itself and its reflection. The flight, quivering and slow, 

 is performed by very slight but rapid strokes of the 



