BATS 43 
pelled to travel on their bellies, they do neverthe- 
less return year after year to the old laying-up 
places. ‘The question of a seasonal movement in 
bats, similar to migration in birds, greatly exercised 
my young mind in former years in a country where 
bats had no business to be. This was the level, 
grassy, practically treeless immensity of the pampas, 
where there were no hollow trunks, nor caves and 
holes for bats to shelter in, nor ruins and buildings 
of brick and stone which would be a substitute for 
natural caverns. Human dwellings were mostly 
mud and straw hovels, and the only trees were those 
planted by man, and were not large and could not 
grow old. The violent winds swept this floor of the 
world, which was unsheltered like the sea. Yet 
punctually in spring the bats appeared along with 
the later bird migrants, and were common until 
April, when they vanished, and then for six months 
no bat would be seen in or out of doors. Clearly, 
then, they were strictly migratory, able like birds 
to travel hundreds of miles and to distribute them- 
selves over a vast area. They were, in fact, both 
migrants and hibernators, since we cannot but 
suppose that they forsook the pampas only to find 
some distant place where they could pass their 
inactive period in safety. 
At one point, about two hundred miles south 
of Buenos Ayres city, the level pampa is broken by 
a range of stony hills, or sierras, standing above 
the flat earth like precipitous cliffs that face the 
sea. On my first visit to that spot I travelled 
