10 



or membranaceous substance ; and that they resembled bone, in their 

 hardening matter being secreted and deposited upon the membrana- 

 ceous substance. It appeared, that the gluten, in the porcellaneous 

 shells, existed in so small a degree of natural inspissation, and was so 

 little advanced in organization, that when the carbonate of lime was 

 dissolved, even by very feeble acids, little or no vestige of jelly, mem- 

 brane, or cartilage could be perceived. In the pearly shells, on the 

 contrary, that substance, which served in the porcellaneous shells 

 merely as a gluten, was not only more abundant, but also more inspis- 

 sated, becoming visible and palpable. This chain of connection 

 between bone and shells, Mr. Hatchett found, was also extended 

 between shells and corals. He found an exact similarity between the 

 substances forming the various shells, and that which forms the various 

 madrepores and millepores ; the nature of these bodies being so com- 

 pletely the same, that the changes or gradations of the one are to be 

 found in the other. Thus some madrepores and millepores, like the 

 porcelaneous shells, afforded a gelatinous substance, on the removal 

 of the carbonate of lime ; whilst others yielded a substance possessing 

 all the characters of the membranaceous substance, contained in the 

 shells formed of nacre or mother of pearl. 



Many of the circumstances which the experiments of Mr. Hatchett 

 have made known, throw a considerable degree of light upon the for- 

 mation of the different animal fossils, and will, therefore, be occasion- 

 ally referred to in the succeeding pages of this work. 



