FROM THALES TO LAMARCK 19 



able whether this fish leaves the water voluntarily for any length 

 of time. 



Evolution having reached this point, the transition to a ' life 

 ashore,' to amphibious animals, was not difficult. But with 

 a sojourn on dry land the extremities are confronted with the 

 solution of fresh and more difficult tasks, and thus we see in 

 the higher vertebrates, especially in the typical terrestrial 

 animals, the Keptiles, Birds, and Mammals, that these organs 

 assume a marvellous wealth of forms and functions. 



It will only be possible for us to consider one order, the lizards. 

 The typical lizards are running animals, possessing five-fingered 

 extremities, but exhibiting great differences according to their 

 different modes of life. The South American Teju (Tupi- 

 nambis teguixin), a large scaly lizard, about 3 ft. long, has 

 assumed the habit of digging, under the roots of trees, deep caves, 

 into which it may retire in a moment of danger. Consequently 

 its front legs are strongly developed and furnished with sharp 

 claws, thus forming powerful digging-tools. In species that live 

 in deserts we frequently find that the toes have been broadened 

 into a shovel-like shape and furnished with lateral fringes so 

 that the animals are* able to run even over the finest sand without 

 danger of sinking into it. Numerous species of Geckos, among 

 them the common Wall Gecko (Tarentola mauritanica), an 

 inhabitant of the Mediterranean countries, are furnished with 

 adhesive digits which enable them to run about on steep, smooth 

 walls, and even on the ceiling. In many districts in Africa 

 Geckos are kept as domestic animals, for as soon as night has 

 come they emerge from their hiding-places to prey on spiders, 

 flies, mosquitoes, and other pests of man. But in spite of their 

 usefulness they are persecuted by man in the most unreasonable 

 manner. 



Typical inhabitants of trees are the Chameleon tidae, famous 

 for their striking colour-changes and fantastic shapes. Their 

 extremities, too, have become transformed corresponding to their 

 mode of life, for in them the toes have grown together in twos 

 and threes into uniform plates (laminae) which stand opposite 

 to each other, as the parts of pincers. They possess, therefore, 

 an ideal gripping and climbing organ by means of which they 

 are able to walk safely even on thin branches. 



