The childhood of animals / by Sir P. Chalmers Mitchell.

  • Peter Chalmers Mitchell
Date:
[1940]
Catalogue details

Licence: In copyright

Credit: The childhood of animals / by Sir P. Chalmers Mitchell. Source: Wellcome Collection.

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    unless they meet death by the way, meet it at the end, after passing through childhood and youth, maturity and old age. This orderly progress from the beginning to the end is char- acteristic of all animals, and the parts of it that we call child- hood and youth are the most characteristic. Complicated pieces of machinery, like watches or motor-cars, resemble animals in many ways, and like 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 diffi- culty 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 Mar-
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