Volume 1

A picture book of evolution / by Dennis Hird.

  • Dennis Hird
Date:
1906-1907
Catalogue details

Licence: Public Domain Mark

Credit: A picture book of evolution / by Dennis Hird. Source: Wellcome Collection.

    140/220 page 128
    working- on the variations offered, we shall not wonder that out of such innumerable varieties of species at least one variety took to living on land. But this was an enormous advance, and must have taken place very slowly. Only by a vast series of small changes was it possible for the structure of a water-breathing animal to become so altered that the animal could live on land and breathe the air. The wonderful con¬ necting-links between the two extremes of fishes on one hand and land animals on the other are called Amphibians. The word means simply a double life—water and land. Amphibians are the class of animals which can live both in water and on land at some stage of their exist¬ ence. As far as living species are concerned, they are the least numer- and the class contains This is a small number mammals, 3,500 reptiles, almost 10,000 birds— (Gadow). The poor amphibians have had their day. It is a long time since they flourished and divided the reign of the world, as far as vertebrates were con¬ cerned, between themselves and the fishes. Fig. 123.—Three distinct Orders. ous of the vertebrates, about a thousand species, compared with the 2,700 over 8,000 fishes, and
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