328 Mr. Hatchett's Experiments on Zoophytes, 



resemble bone in a considerable degree, as they consist of a 

 gelatinous, cartilaginous, or membranaceous substance, forming 

 a series of gradations, from a tender and scarcely perceptible 

 jelly to membranes completely organized, in and upon which 

 carbonate of lime is secreted and deposited, after the manner 

 that phosphate of lime is in the bones ; and therefore, as the 

 porcellaneous shells resemble the enamel of teeth, so the shells 

 formed of mother of pearl, &c. in like manner resemble bone ; 

 the distinguishing chemical character of the shells being car- 

 bonate of lime, and that of enamel and bones being phosphate 

 of lime, 



3dly. It was proved, that the crust which covers certain 

 marine animals, such as crabs, lobsters, crayfish, and prawns, 

 consists of a strong cartilage, hardened by a mixture of carbo- 

 nate and phosphate of lime ; and that thus these crustaceous 

 bodies occupy a middle place between shell and bone, although 

 they incline principally to the nature of shell. And, 



4,thly. It was proved, that a certain portion of carbonate of 

 lime enters the composition of bones in general ; the proportion 

 of it however being, to the phosphate of lime, vice versa to that 

 observed in the crustaceous marine substances. 



Upon the view, therefore, of these facts, it is evident, that 

 there is a great similarity in the construction of shell and bone; 

 and that there is even an approximation in the nature of their 

 composition, by the intermediate crustaceous substances. 



These remarks, with the experiments by which they are 

 supported, form the principal features of that paper, which the 

 Royal Society honoured with a place in the last volume of 

 the Philosophical Transactions. At that time, it was not my 



