INTRODUCTION. XVII 
Yellow Boas, Chilabothrus mornatus, in my possession have been repeatedly 
heard to give utterance to a low plaintive whine as the breath has been 
forcibly emitted. Apparently it is by the sense of smell that the snake finds 
its companion. About the time of coupling many species are possessed of a 
powerful and very disagreeable odor.” The sense of taste is probably lack- 
ing. The tongue is a tactile organ; it is soft, slender, provided with a pair 
of flexible tips, and can be retracted into a sheath at the bottom of the 
mouth. As serpents move about they are constantly feeling ahead of them 
with the tongue, and the forward thrust and peculiar appearance of this 
organ has given rise to the false idea that with it the “stinging” is done. 
The stomach is formed by a widening of the alimentary canal; its sides are 
thicker than those of the esophagus, and have longitudinal folds. Diges- 
tion is quick or slow according to the temperature; venom hastens the 
process. One lung is often rudimentary; in species of Boa, Naja, and 
Crotalus, both are developed; in Boa they are about equal in size. The 
ovaries and testes are paired, the right often larger and placed a little in 
advance of the left. The male is furnished with a pair of intromittent 
organs, one of which is placed on each side of the vent under the base of 
the tail. They are tube-like, and bear a groove on the side; when in use 
they are everted like the finger of a glove, and the groove becomes an 
external furrow by which the seminal liquid is conducted into the oviduct. 
Careless observers have mistaken these organs for feet. In certain species 
their extremities are surrounded by series of strong, sharp spines or hooks. 
The eggs are oblong, and have a soft, leathery envelope, for the rupture of 
which in hatching the young are provided with an ege-tooth. Oviparous 
serpents generally leave the eggs to hatch and care for themselves; the 
Pythons or rock snakes of the Eastern Hemisphere are exceptions to this 
rule; after the eggs are laid the female coils her body round them and incu- 
bates. Viviparous species are those in which the eggs are hatched in the 
oviduct; there are those in which hatching and laying happen so nearly at 
the same time that they are at times oviparous and at others apparently 
viviparous. The ribs are very numerous, in some species numbering hun- 
dreds, and are loosely articulated to the vertebrae. They furnish the main 
dependence in locomotion. In reality, there are three methods of progres- 
sion used by Ophidia, and each of these may be employed separately. 
When a serpent glides he brings the lower ends of opposite ribs forward 
Mem.— yor 1—2 
