X INTRODUCTION". 



possession of rudiments of limbs not visible externally. A few lizards 

 have the ears covered by the skin, and others have no eyelids. There are 

 serpents and lizards which have similar forms, motions, and habits. The 

 extent of variation may best be seen by comparison of the examples cited 

 below. 



Development of the senses varies accoi'ding to hal)its. In the seri:)ent- 

 tongucd lizards we meet with great quickness of sight, hearing, scent and 

 touch, accompanied by lack of taste — the tongue simply being a very sen- 

 sitive tactile organ. Again, in species living upon vegetation, the touch is 

 deficient and the tongue is short and thick, evidently an organ of taste. 

 The keen-sighted Chamaeleon has a tongue which is probably an organ 

 of taste as well as touch. 



Many of the Saurians are noted for transient variations of color. The 

 cause of these changes is found in the presence of pigments of different 

 colors at various depths below the surface of the skin. The expansion or 

 contraction of one or more of the layers, in consequence of muscular action, 

 nervous irritation, or contraction or inflation of the lungs, changes the pro- 

 poi'tion of the different pigments visible at a particular instant. If the 

 upper layer contains the dark pigment, the contraction of its chromato- 

 phores lessens the visible amount of this color and exposes a gi*eatcr amount 

 of tliat beneath it. These changes are not to be confounded with that occur- 

 ring on soils of light color, or in regions Avhere there is great reflection of 

 the rays of light; in such localities permanent lightening of the colors is 

 apparently due to a Ijlcaching process undergone by the pigments. It seems 

 as if the effect of polarized light upon the pigment diflered from that of the 

 direct unpolarized rays. Commonly each vertebra is concave in front and 

 cnn^•ex l)ehind. To this there is a very marked exception in the case of the 

 RiiYNCHocEPHALiA, a suborder founded on a family represented I)y a single 

 genus of New Zealand lizard, Ilatteria or S2)henodon. Externally this ani- 

 mal resembles the species of tlie European genus Lacerta so much that one 

 can hardly believe it more than genei'ically distinct. Skeletal structure and 

 details of anatomy discover differences of sufficient importance to warrant 

 the estal>lishment of a different order. Most noti('eable of its peculiarities 

 are the series of jjalatine teeth, the structure of the skull, the biconcave 

 vertobrpe, the presence of a cartilaginous rib beneath each transverse fold 

 of tlie skin of the abdomen, and the absence on the male of intromittent 

 sexual organs. 01' those examined the females were lighter in color, and 



