distinct genera inhabit the same districts, and are so like each other
that no one but a naturalist would distinguish the harmless from the
poisonous kinds. Hence, as Mr. Wallace believes, the innocuous kinds
have probably acquired their colours as a protection, on the principle
of imitation; for they would naturally be thought dangerous by their
enemies. The cause, however, of the bright colours of the venomous
Elaps remains to be explained, and this may perhaps be sexual
selection.
Snakes produce other sounds besides hissing. The deadly Echis carinata
has on its sides some oblique rows of scales of a peculiar structure
with serrated edges; and when this snake is excited these scales are
rubbed against each other, which produces a curious prolonged, almost
hissing sound. (63. Dr. Anderson, Proc. Zoolog. Soc. 1871, p. 196.)
With respect to the rattling of the rattle-snake, we have at last some
definite information: for Professor Aughey states (64. The American
Naturalist, 1873, p. 85.), that on two occasions, being himself
unseen, he watched from a little distance a rattle-snake coiled up with
head erect, which continued to rattle at short intervals for half an
hour: and at last he saw another snake approach, and when they met they
paired. Hence he is satisfied that one of the uses of the rattle is to
bring the sexes together. Unfortunately he did not ascertain whether it
was the male or the female which remained stationary and called for the
other. But it by no means follows from the above fact that the rattle
may not be of use to these snakes in other ways, as a warning to
animals which would otherwise attack them. Nor can I quite disbelieve
the several accounts which have appeared of their thus paralysing their
prey with fear. Some other snakes also make a distinct noise by rapidly
vibrating their tails against the surrounding stalks of plants; and I
have myself heard this in the case of a Trigonocephalus in S. America.
LACERTILIA.
The males of some, probably of many kinds of lizards, fight together
from rivalry. Thus the arboreal Anolis cristatellus of S. America is
extremely pugnacious: During the spring and early part of the summer,
two adult males rarely meet without a contest. On first seeing one
another, they nod their heads up and down three or four times, and at
the same time expanding the frill or pouch beneath the throat; their
eyes glisten with rage, and after waving their tails from side to side
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