34 



teresting and important conjectures. Correct investigation 

 is therefore demanded : a careful comparison of the re- 

 spective characters of these substances must be made, and 

 the various circumstances belonging to their present ex- 

 traneous situations be endeavoured to be ascertained. 



Zoophijtes. — These substances, possessing an animal na- 

 ture under forms approaching to those of vegetables, fre- 

 quently occur in a mineralized state. The inquiries re- 

 specting them will, for obvious reasons, be first directed to 

 those which are of the simplest forms and structure. 



Sponge is, in its recent state, a polymorphous, soft, 

 porous, flexible and elastic body, manifesting a small portion 

 of irritability and vitality. It is composed of fibres of a 

 peculiar substance disposed rather in a membranaceous 

 form, blended with minute spicules of various figures ; the 

 whole connected in a variously formed network, and in- 

 vested by a light gelatinous matter. 



Count Marsilli, who had the most favourable oppor- 

 tunities of examining into the nature of this substance, was 

 satisfied, although led to the belief of its being a vegetable, 

 that he had many times observed a regular systole and 

 diastole taking place in some of its more circular apertures. 

 Hut neither M. Peron nor M. Bosc have been able to con- 

 firm these obervations*. 



* The following remarks on the nature of this substance merit 

 attention : — Although the animal nature of sponge is generally ad- 

 mitted, no circumstance which may serve to illustrate its history, 

 and tend to dispose of it in its proper place in the system of nature, 

 should be unnoticed. The following observations of Dr. Fyfe may 

 indeed be considered as adducing very important evidence on this 

 subject. Sir Humphrey Davy had procured iodine from several of 

 the fuci and ulvae, but not from the alkaline matter manufactured 

 at Sicily, Spain, and the Roman states, nor did he find that the 

 ashes of coral or of sponge appeared to contain it. From various 

 experiments Dr. Fyfe was enabled to conclude that iodine was 

 confined not only to the class crj^jtogamia, but to the marine pro- 



