§ 13. NATURE OF CORAL ZOOPHYTES. 609 



during the decomposition of the animal matter. It is now 

 a calcareous skeleton, with here and there portions of the 

 shrivelled integument, but, of course, without any traces of 

 polypes in the cells. 



Let us now refer to our previous remarks, and inquire if 

 the Flustra presents the essential characters of animal ex- 

 istence. Its polype possesses a determinate form, and has 

 a calcareous skeleton covered by a soft fleshy substance, 

 that can for a certain period resist chemical and mechanical 

 agency. It is furnished with instruments capable of moving 

 with great celerity, is susceptible of external impressions, 

 and can expand and contract at will. Here, then, is evidence 

 of sensation and of voluntary motion ; and although, from 

 the extreme minuteness of the structure, nerves cannot be 

 detected, yet there can be no doubt that it possesses 

 a nervous, and also a circulatory system for effecting nutri- 

 tion and reparation. We find, also, that when removed 

 from the element in which it lived, the creature dies, and its 

 soft substance, like the flesh of the larger animals, undergoes 

 putrefaction; it has lost the vital principle by which it pre- 

 viously resisted chemical agency, and now submits to the 

 effects of those laws which act upon inorganic matter ; the 

 calcareous materials that composed its skeleton, and which, 

 like the bones of mammiferous animals, were secreted by the 

 soft parts, alone remain. 



I would here particularly remark, that the stony support 

 of all Zoophytes is formed by a similar process ; the hard 

 substance called coral, being secreted by the integuments, or 

 membranes with which it was permeated and invested, in 

 like manner as the bones and nails in man are secreted by 

 the tissues designed for that purpose, and acting without 

 his knowledge or control. Nothing can be more erroneous 

 than the popular notion that the cells of corals are built up 

 by the polypes found in them, in the same manner as are 

 the cells of wax by the Bee. 



From what has been advanced, it is evident that the 



