3H Mr. Hatchett’s Experiments 
effervescence was produced, and a thin external stratum was 
dissolved; after which, it remained in a perfectly coriaceous state, 
and complete, in respect to the original figure. 
The dissolved portion, being examined by the usual precipi- 
tants, proved to be carbonate of lime, without any mixture of 
phosphate ; but, in another species of the Asterias, which had 
twelve rays, ( Asterias papposa,) I discovered a small quan- 
tity of phosphate of lime. I am therefore induced to sus- 
pect, that in the different species of the Asterias, nature makes 
an imperfect attempt to form shell on some, and a crustaceous 
coating on others; and that a series of gradations is thus formed, 
between the testaceous, the crustaceous, and the coriaceous 
marine animals. 
It was now requisite to ascertain if phosphate of lime is a 
component part of the substance which covers the crustaceous 
marine or aquatic animals, such as the crab, lobster, prawn, 
and crayfish. 
Pieces of this substance, taken from various parts of those 
animals, was, at different times, immersed in acetous, and in 
diluted nitric acid ; those which had been placed in the diluted 
nitric acid, produced a moderate effervescence, and in a short 
time were found to be soft and elastic, of a yellowish-white 
colour, and like a cartilage which retained the original figure. 
The same effects were produced by acetous acid, but in a less 
degree ; in the latter case also, the colouring matter remained, 
and was soluble in alcohol. 
All the solutions, both acetous and nitric, afforded carbonate 
and phosphate of lime, although the former was in the largest 
proportion. 
There is reason to conclude, therefore, that phosphate of lime, 
mingled with the carbonate, is a chemical characteristic which 
