104 The Naturalist in La Plata. 
Assuming that these two young bats had, before 
I found them, existed like parasites clinging to the 
parent, their adroit actions when liberated, and 
their angry demonstrations at my approach, were 
very astonishing; for in all other mammals born 
in a perfectly helpless state, like rodents, weasels, 
edentates, and even marsupials, the instincts of 
self-preservation are gradually developed after the 
period of activity begins, when the mother leads 
them out, and they play with her and with each 
other. In the bat the instincts must ripen to per- 
fection without exercise or training, and while the 
animal exists as passively as a fruit on its stem. 
I have observed that the helpless young of some 
of the mammals I have just mentioned seem at first 
to have no instinctive understanding of the lan- 
guage of alarm and fear in the parent, as all young 
birds have, even before their eyes are open. Nor 
is it necessary that they should have such an 
instinct, since, in most cases, they are well con- 
cealed in kennels or other safe places; but when, 
through some accident, they are exposed, the want 
of such an instinct makes the task of protecting 
them doubly hard for the parent. I once surprised 
a weasel (Galictis barbara) in the act of removing 
her young, or conducting them, rather ; and when 
she was forced to quit them, although still keeping 
close by, and uttering the most piercing cries of 
anger and solicitude, the young continued piteously 
crying out in their shrill voices and moving about 
in circles, without making the shghtest attempt to 
escape, or to conceal themselves, as young birds 
do. 
