61 
the carnivora sleep for the most part by day, and 
seek their food by night: the herbivora feed and 
sleep at intervals by day and by night. Total dark- 
ness, however, suspends all activity. Moonlight, on 
the other hand, calls forth the squirrel tribes to 
sport in the summer, and guides wolves, the cat 
tribes, and the aquatic carnivora, to their prey. The 
Scythian antelope® is said to feed by intervals, which 
appear to be regulated by a sort of covenant. Some 
of the herd are constantly on the watch while the 
others sleep: when those of the first watch become 
weary, they give a signal to those who have slept, 
who quickly rise and relieve guard. The eyes of 
many quadrupeds, especially of the feline tribe, are 
offended by strong light : those which feed with the 
eyes downward are unwilling to gaze upward. Sheep 
form circles, turning their heads towards a centre, 
which is darkened by the shadow of those whose 
tails are turned to the sun. Kangaroos are said to 
possess nictitating membranes like those of owls, &c.: 
they lower their fore-legs when feeding. The dew 
on the grass and leaves of plants induces most of the 
herbivora to feed at the hours of twilight. Observa- 
tions on the wintry sleep or torpor of many genera 
must be deferred till I consider the subject of hy- 
bernation. A strongly marked division of birds is 
notoriously nocturnal; that is to say, feeds almost 
wholly by twilight or moonlight. Yet more than 
one order, family, and genus, has its night feeders: 
owls, of the order raptatores; caprimulgus, of the 
© Saiga, Linneus, and Buffon. 
