2 CHILDHOOD OF ANIMALS 



characteristic of all animals, and the parts of it that we call childhood 

 and youth are the most characteristic. Complicated pieces of 

 machinery, like watches or motor-cars, resemble animals in many 

 ways, and hke them may be new or old, but are never young. 

 Youth is a property of the living world. 



The history of an animal, from its first appearance as a speck 

 of living matter formed from the parental body, to its death, is 

 continuous, and it would be useless to try to define exactly when 

 childhood begins, when it passes into youth, or the point at which 

 the period of youth ends. There is difficulty even in fixing the 

 beginning, for animals of the same kind may be born at different 

 stages of growth, whilst animals of different kinds differ extremely 

 in this respect. A large black newt, brilliantly spotted with yellow, 

 known as the spotted salamander and common in the south of 

 Europe, lays eggs like the spawn of a frog. But unlike the eggs of the 

 frog which show the presence of tadpoles only after some days, those 

 of the salamander appear with fully formed little tadpoles wriggling 

 in them, and hatch almost as soon as they are laid. Sometimes 

 they hatch actually before they are laid, and it is in the tadpole 

 stage that the animals first appear in the world. So also most 

 snakes lay eggs and incubate them for days or weeks, before 

 the young snakes break through the leathery shell. But in some 

 snakes, like the common adder, what corresponds to hatching takes 

 place inside the body of the mother, and instead of eggs being laid, 

 young snakes are born. Most of the warm-blooded, hairy creatures 

 that we know as mammals because they suckle their young, give 

 birth to moving young and do not lay eggs, but two of them, the 

 duck-billed platypus and the spiny echidna of Australia, lay eggs 

 with yolk and hard shells. The platypus incubates the eggs until 

 they hatch ; the echidna, after laying an egg, transfers it with her 

 mouth to a pouch on the under side of her body, like that of a 

 kangaroo, and in this warm and secure receptacle, safer than any 

 nest, the egg is kept until it hatches. Mammals of the group 

 known as Marsupials, because most of them have a marsupium, or 

 pouch (which is well seen in the kangaroo), at one time laid large 

 eggs and no doubt transferred them with the mouth to the pouch, just 

 as the echidna still does. But now the eggs are retained for a certain 

 time in the body, although the young are still very imperfect when 

 they are born. The new-born young of a kangaroo is less than an 

 inch long, although its mother may be nearly as tall as a man. The 

 figure (Fig. i) has been drawn from a specimen obtained at the 



