446 Fretp Museum or Natura History — Zoétocy, Vor. XI. 
The hairs of Bats often show a decided difference in structural 
characters in members of different families. In some species of Mo- 
losside, for example, the hair when viewed under a powerful microscope 
shows zones or rings of verticulate spinules (Fig. a), while in many 
species belonging to the family Vespertilionide the spinules or scales are 
arranged in a continuous spiral (Fig. 6), or in irregular imbricated tri- 
angles (Fig. d). Judging from a number of specimens I have examined, 
while the hairs of Bats belonging to allied species seem to be of the 
same general pattern, they are by no means alike and there is usually 
considerable variation even in hairs from the same animal. 
‘a b c d e 
Hairs of Bats. 
a, Nyctinomus depressus; b, Pipistrellus subflavus; c, Myotis californicus; d, Lasionycteris nocti- 
vagons; e, Corynorhinus macrotis. (Greatly enlarged.) 
Bats differ widely in appearance and mode of life from other mam- 
mals and their place in Nature was a debatable question among the 
older naturalists. Aristotle defined them as birds with skinny wings; 
Pliny also considered them birds, although he states that the young 
are born alive and suckled by the mother. Later writers recognized 
them as mammals, but differed as to their classification. Linnaeus 
ranked them with the Primates on account of the number of upper 
"incisors (supposed at that time to be always 4), the thoracic position 
of the mamme, the placental, uterine, and other anatomical char- 
acters. Prof. Huxley, however, later considered them to be merely 
greatly modified Insectivora but representing a well marked order, 
and his opinion has generally been accepted by modern zodlogists. 
Bats are gregarious, nocturnal and crepuscular. They sleep most 
of the day gathered together in dark places, such as caves, hollow trees 
and in old buildings. When at rest they usually suspend themselves 
by the claws of their hind feet and hang head downward. They 
are unable to move about on the ground except with much difficulty, 
largely on account of the peculiar structure of their hind legs (the 
knee bending backward instead of forward), and when forced to do 
