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 may 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 



