SUB-KINGDOM VIII. 

 THE COELENTERATA. 



SPONGES, CORALS, ETC. 



By IIenky M. Bernard, M.A., F.L.S., Etc., akd Matilda Bernard. 



The Coelenterata are to be distinguished from all the animals hitherto 

 described by the fact that the alimentary canal no longer runs through the 

 body as a free tube suspended to its walls and surrounded by the body cavity. 

 Animals in which such a closed alimentary canal is found are known as the 

 Coelomata, on account of the spaces between the canal and the body wall. 

 In contradistinction, the Coelenterata or hollow-bodied animals are called 

 the Acoelomata, because the digestive sac fills up the whole body without 

 leaving any spaces between the digestive layer and the body wall. The body 

 is, in fact, a more or less simple sac into which the mouth opens. 



The Coelenterata, while thus distinguished from all animals higher than 

 themselves, are nevertheless associated with them owing to the multicellular 

 c imposition of the body. As Metazoa, or many-celled animals, they diifer 

 from all lower animals or Protozoa, whose bodies are unicellular. 



The Coelenterata may be divided into two groups — (1) the Sponges, and (2) 

 the Cnidaria. 



I. — The Sponges. 



The Sponges, which are also known as the Porifera, on account of the 

 pores that perforate their walls, are usually considered to be Coelenterates of 

 a very simple kind, although many naturalists place them in a group by 

 themselves. 



The Sponges have been the subject of frequent discussion among naturalists 

 from the time of Aristotle down to the present day. Aristotle was of opinion 

 that they were animals, because they appeared to shrink when torn from the 

 rocks, and thus seemed to show signs of sensation, but their real nature was 

 altogether misunderstood by most of the earlier naturalists, some considering 

 them to be plants, others congealed foam of the sea. Lamarck, even, 

 imagined the apertures on the surface of a Sponge to be the mouths of cells 

 occupied by small polyps something like the Coral polyps, which, however, 

 could never be discovered in their homes. Peysonnel, on the other hand, 

 considered a large worm which often lives In Sponges to be their "sole 

 fabricant, the rest being mere nidus or excretion." About one hundred and 

 fifty years ago the secret of Sponge life was revealed when the fact that 

 water is drawn into the Sponge and expelled by it was established, but the 

 various ways in which the currents of water pass through the body, and their 

 relation to the life of the Sponge, were not accurately investigated until about 

 seventy years ago, and are, indeed, still to a certain extent problematical. 



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