310 Proceedings of Royal Society of Edinburgh. [may 7, 
It was this question which led us to believe that the sulphate of 
lime, present in such abundance in sea water, might he assimilated 
by marine animals, and during digestion, elaborated as carbonate of 
lime. This view we find is entertained by others, for Dana, in 
his book on Coral and Coral Islands, p. 99, writes: — “The sea 
water and the ordinary food of the polyps are evidently the 
source from which the ingredients of coral are obtained. The 
same powers of elaboration which exist in other animals belong to 
polyps, for this function, as has been remarked, is the lowest attri- 
bute of vitality. Neither is it at all necessary to inquire whether the 
lime in sea water exists as carbonate or sulphate, or whether chloride 
of calcium takes the place of these. The powers of life may make 
from the element present whatever results the functions of the 
animal require.” 
Mr J. Y. Buchanan, in a paper read before the British Associa- 
tion in 1881, p. 584, suggests, that the “testaceous denizens of the 
sea assimilate their lime from the gypsum dissolved in sea water, 
forming sulphide of calcium in the interior of the animal, which is 
transformed into carbonate of lime on the outside.” 
Not having the means of experimenting upon coral polyps, we 
instituted a series of experiments which we hoped might help by 
analogy to prove the fact that animals have the power of 
elaborating carbonate from the other salts of lime. 
On the 31st of January of this year, two hens and a cock were 
shut into a room lined throughout with wood, where it was impos- 
sible that they could obtain lime in any other form than that given 
to them in their food. Each had 5 oz. of food per diem, and along 
with this were given 100 grains of pure h}Mrated sulphate of lime, 
their drink being distilled water. (The total lime calculated as 
carbonate in the ash of their food amounted as determined to less 
than 1-4074 grains in each ration.) 
During the six weeks they were subjected to this treatment 
twenty-three eggs were laid, two of which were very thin in the 
shell, but the rest were in all respects normal. The shells on being 
analysed were found to consist of carbonate of lime, organic matter, 
and water. 
After removal of the membranous lining of the shells and drying 
