306 BATS: 
During the daytime these bats repose in caves or hollow trees, whence they 
issue forth for their nightly blood-sucking. It appears that when they have 
selected a victim for attack, they either settle down on or hover over the part 
to be operated on; and then proceed to shave away a thin portion of skin by a 
razor-like action of the sharp upper incisor teeth, by which the blood is caused to 
ooze from a number of the small capillary vessels, and is then sucked up by the 
mouth and swallowed. From their structure, it is probable that blood constitutes 
their whole diet. 
The fact that certain bats in South America were veritable blood-suckers 
has been long known; our first information dating from a period soon after the 
conquest of that country. Great uncertainty prevailed, however, for a lengthened 
period as to which particular species of the large family of vampires were the 
real culprits; and the question was not finally decided till, during the voyage of 
the “ Beagle,’ Mr. Darwin had the good fortune to see a desmodus caught in the 
very act. His account has been quoted over and over again, almost ad nauseam, 
and we shall refrain from repeating it here; merely mentioning that the bat in 
question—which was the common blood-sucking vampire—was caught by one 
of the great naturalist’s servants actually sucking the blood from the withers 
of one of the camp horses. ‘Thus was set at rest for ever the long vexed question 
as to which was the true blood-sucking vampire. It may be observed, however, 
that whereas it is now certain that the present group is the only one of which the 
members subsist entirely on a diet of blood, yet it is possible that, as already 
mentioned, some of the javelin-bats or their allies may, on occasions, vary their 
ordinary food with it. 
Fossit Bats. 
From the exigencies of space our account of the bats has been somewhat brief ; 
but it may serve to show what an extensive assemblage of animals it really 
includes, and how different from one another in habits, as well as in details 
of structure, are many of its members, though all bats agree very closely in their 
general plan. This conformity to a common structural standard is as fully 
characteristic of the few fossil bats with which we are at present acquainted, as 
it is of their modern allies; the whole of them belonging to living families, and a 
large proportion to existing genera. At the comparatively early period when the 
Upper Eocene strata of the Paris basin were deposited, leaf-nosed bats, as well 
as typical bats nearly allied to the living noctule, had already come into existence, 
and have left their remains buried in the rocks alongside those of strange extinct 
hoofed mammals, such as the Paleotheres and Anoplotheres. And it is, there- 
fore, manifest that if we ever succeed in discovering the ancestral forms from 
which bats have been derived, it will be in rocks of far greater age than those of 
the Paris basin, which belong to the lower portion of the Tertiary period of 
geological history. It is, indeed, within the bounds of probability that bats have 
existed as such from a period as remote as the one during which the English chalk 
was deposited on the floor of an ancient ocean. 
