CHAPTER IV. 



Reptiles. 



REPTILES (from Latin repo, " I creep ") are represented in Great Britain by 

 very few species. They are cold-blooded animals that is, the temperature 

 of the blood is much lower than that of mammals or birds. They do not 

 pass through any such changes as in the life-history of the frog, but the young 

 are like their parents, differing only in size, and they breathe by means of 

 lungs. Two classes or sub-orders of reptiles are known to us in Great Britain 

 the Ophidia, serpents ; and Lacertilia, lizards. The latter have jaws so 

 connected that they cannot be distended ; but the serpents have jaws joined 

 together by an elastic ligament which allows them to be opened to such an 

 extent that they can swallow far larger victims (such as frogs and mice) than 

 at first would seem possible. 



The skin of reptiles is a characteristic feature : the upper, or epidermis, 

 is in reality of a very thin and transparent, horny nature, and looks like scales, 

 like those of fishes. It is shed, or cast off, by the reptiles, from time to time, 

 and very often you may find the skin of a snake, very fragile and light, lying 

 where it has been discarded by its owner. 



Most lizards have four legs ; but one the Blind Worm be it noted, 

 has no external limbs, and so is often mistaken for a snake. They are coloured 

 in such a way as to harmonize with their surroundings (many other instances 

 of " protective coloration " are given in this book), the result being that it 

 needs an experienced eye to distinguish them when motionless. A dry heath 

 or a sunny bank is the place to find them, but the slightest unwary move- 

 ment will cause them to vanish from sight. It is well known that when 

 caught a lizard will frequently snap off the end of its tail in the hope of escap- 

 ing. After a time the injured portion grows again to more or less of its original 

 state. 



Some reptiles are oviparous that is, they lay eggs from which the young 

 are hatched ; others are viviparous, bringing forth their young alive ; and 

 still others are ovo-viviparous, laying eggs in which the young are already well 

 developed and about to hatch out. 



Sub-order : LACERTILIA Lizards. 



Only three species are found in the British Isles. 



i. The Common Lizard (Zootoca vivipara], to be found on banks, heaths, 



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