INTRODUCTION". XVII 



Yellow Boas, CMlabothrus inornatus, 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 oesophagus, 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 egg-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 vertebra?. 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. — voi, n — 2 



