362 Mr. Hatchett's Experiments on Zoophytes, 



which were noticed in the Patella, correspond precisely with 

 the Madrepores and Millepores which afford a gelatinous sub- 

 stance ; and lastly, the characters of the membranaceous part, 

 exhibited by the shells formed of nacre or mother of pearl, are 

 in like manner to be found among some of the Madrepores 

 and Millepores, such as Madrepora ramea, Millepora fascialis, 

 Millepora truncata ; for these, like the Turbo olearius and Ha- 

 liotis Iris, are composed of a fibrous membrane, hardened by 

 carbonate of lime. 



It appears therefore, that the Madrepores and Millepores, like 

 the various shells, are formed of a gelatinous or membrana- 

 ceous substance, hardened by carbonate of lime ; and the only 

 difference is in the mode according to which these materials 

 have been employed. 



The experiments on Tubipora musica proved, that in compo- 

 sition it resembled the foregoing substances. But a slight diffe- 

 rence was observed, in respect to the hardening substance of 

 Flustra foliacea and Corallina Opuntia; for a small portion of 

 phosphate was found mixed with the carbonate of lime ; but the 

 membranaceous part of these bodies resembled that of certain 

 Madrepores and Millepores, particularly Millepora fascialis. 



Two species of Isis were next examined, namely, Isis ochracea 

 and Isis Hippuris : both of these were proved to be formed of 

 regularly organised membranaceous, cartilaginous, and horny 

 substances, hardened, in the last mentioned species, merely by 

 carbonate of lime; but, in the Isis ochracea, with the addition of a 

 very small portion of phosphate of lime. 



The subsequent experiments were made on various species of 

 Gorgonia, and first on Gorgonia nobilis, which was formerly 

 regarded as an Isis. 



