Page:British Reptiles, Amphibians, and Fresh-water Fishes.djvu/21

INTRODUCTION bygone reptiles have occupied in the past history of the world.

Some kinds of reptiles still existing are equally well at home on land or in water, and there are others which spend part of their time on one and the remainder in the other. Snakes can and do take to water, though this was for long disputed, but, as a rule, the Grass Snake is more fond of this than the Adder, which exhibits a liking for dry situations. Matrix, the specific name of the Grass Snake, means Water Snake, and it should be stated that all Snakes are fond of drinking. Whilst Snakes and Lizards are closely related, there are easy distinguishing features, such as the absence in Snakes of any functional limbs, and also the absence of eyelids. The eye of a Snake has only a thin transparent covering, and when, as happens, a Snake changes its skin, this covering peels off in the form of a lens. On the other hand the Slow, or Blind, Worm is not a Snake, and it is certainly not a Worm. Neither is it blind. It is a legless Lizard, having distinct eyelids. There are other anatomical differences between the two Orders dealt with in this first section, but these need not detain us, and it only remains to be recorded that the greater majority of the creatures contained in the Class Reptilia deposit eggs, which are oblong in shape, and have a soft leathery covering, or shell. In some kinds of Snakes, however, especially those inhabiting fresh and salt water, and also Lizards, the eggs are hatched within the parent's body. This is so in the case of our own British Adder, 5