Elementary biology : descriptive and experimental / by John Thornton.

  • Thornton, John
Date:
1907
Catalogue details

Licence: In copyright

Credit: Elementary biology : descriptive and experimental / by John Thornton. Source: Wellcome Collection.

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    by which the honey of flowers is sucked up (Figs. 5 and 94). A bee has also a kind of tubular trunk, but it is much shorter than that of a butterfly or moth, and cannot, like that of those insects, be rolled up (Fig. 93). The highest or primary group of ani- mals is termed the Vertebrata, and includes all the animals possessing an internal skeleton with a flexible back- bone, a true brain in the head, a spinal cord, and a gradually increasing and specialized nervous system. The subdivisions of the group of Fig. 5-Head of moth, Vertebrata are: (a) fishes; (b) amphi- turned^up and^ bians (frogs, toads, etc.); (c) reptiles tons labial (snakes> lizards, etc.); (d) birds and (e) paips between the mammals. By comparing these sub- eyes, ihe proboscis ... J ° partly coiled is also divisions of the vertebrata we find a shown. (From Mac- . . ... aiister’s “ Zoology of gradually increasing complication of Invertebrate Ani- . ... ... mais.”) structure and a corresponding specializa- tion of work in various organs, the great life-processes not only having distinct parts of the body devoted to them, but subsidiary processes having special parts executed by distinct organs. (As a good example of increased specialization and division of labour, compare the structure and work of the simple digestive canal of a mollusc like the oyster with that of a quadruped like the cat (see Figs. 4 and 146)). The Mammalia or suck-giving animals form the highest group in the Animal Kingdom, since they possess the most complex organization adapted to perform the greatest number and variety of actions with the most advantage to the individual. There is in them, in other words, the greatest physiological division of labour. They breathe by lungs in which the air-tubes terminate in air-cells, they have a heart that provides for a double circulation, and the thorax and
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