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. Natrix, 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, 
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