44 THE BOOK OF A NATURALIST 
with a party of eight or nine gauchos, and evening 
coming on near our destination, we camped about 
a league from the foot of the hills and built a big 
fire. Just as we had got a good blaze a loud cry 
of “ Morcielagos!” (bats) from one of the men 
made us look up, and there, overhead, appeared a 
multitude of bats, attracted by the glare, rushing 
about in the maddest manner, like a cloud of 
demented swifts. In a few moments they vanished, 
and we saw no more of them. Bats, I found, were 
extremely abundant among these hills, and here 
they were probably non-migratory. 
But the main question about bats is always that 
of their sense-organs, in which they differ not only 
from all other mammalians but from all verte- 
brates, and if in this there is any resemblance or 
analogue to any other form of life it is to the 
insect. As to insect senses we are very much in 
the dark. The number of them my be seven or 
seventeen, since insects appear to be affected by 
vibrations which do not touch us. We exist, it 
has been said, in a bath of vibrations; so do all 
living things; but in our case the parts by which 
they enter are few; so too with all other verte- 
_ brates except the bat alone, and a puzzle and 
mystery he remains. What, for example, are the 
functions of the transverse bands on the wings 
formed of minute glands; the enormous expanse 
of ears in the long-eared bat; the earlet, a curious 
development of the tragus; and the singular leaf- 
like developments on the nose of the horseshoe 
