Identifier: royalnaturalhist612lyde (
find matches)Title:
The royal natural historyYear:
1893 (
1890s)Authors:
Lydekker, Richard, 1849-1915 Sclater, Philip Lutley, 1829-1913 Frostick, W. B., former owner. DSI Brooks, W. T., former owner. DSISubjects:
Zoology Natural historyPublisher:
London and New York : Frederick Warne & Co.Contributing Library:
Smithsonian LibrariesDigitizing Sponsor:
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view book online to see this illustration in context in a browseable online version of this book.Text Appearing Before Image:ly a system of cavities, allin open communication with one another, occupying almost every corner of thebody. Again, the Coelenterates are radiate in structure, that is, when seen from above,they are typically star-shaped; and if a Ccelenterate be cut across, every horizontalsection shows a symmetrical arrangement of the parts around a centre. There areother radiate animals, such as the Echinoderms, but while in these five is thefundamental number of rays, in the Coelenterates the rays are often far morenumerous, being some multiple of four or six. Again, while the skin of the formeris almost always modified into a skeleton, or is thick like leather, leathery skins arethe exception in the latter. When the Coelenterates do form calcareous skeletalstructures, these are quite different from the tests of the sea-urchins; and, in allss, the anterior end of the body, crowned with one or more circles of tentacles,remains soft and flower-like. The most highly developed of the free forms, how-Text Appearing After Image:CTENOPHORES. CTENOPHORES. 4 7 5 ever, such as the sea-anemones and the jelly-fish, have no hard skeleton at all, butare amongst the most delicate and beautiful objects in the realm of living nature. In spite of the variety of forms to be found, the Coelenterata are almost asincapable of higher development as the Echinoderms. Like the latter, they havefailed to make any way in fresh water, not to speak of the land. A few free-swimming jelly-fish, a minute attached polyp, and some degenerate sponges are,indeed, found in fresh water, but these can hardly be looked upon as successes.While, at present, it is not easy to connect the Coelenterata with any other group,inasmuch as they appear to stand without any near relatives among the higheranimals, they have a special interest, since they are considered to represent a stagein the development of animal life through which all the higher forms have passed.Some simple form of Coelenterate may have given rise to all the higher animalforms, theNote About Images Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original work.