1889-90.] Dr J. Murray & Mr R. Irvine on Coral Reefs. 85 
During the past few years a large number of experiments have 
been carried on at the Scottish Marine Station for Scientific Research, 
with the view of throwing some additional light on the oceanic 
phenomena referred to in the preceding paragraphs, in so far as these 
relate to the secretion and solution of carbonate of lime under vary- 
ing conditions. Those dealing with the secretion of carbonate of 
lime by organisms will be considered in the first place, and after- 
wards those treating of the solution of the dead carbonate of lime 
shells and skeletons will be discussed. 
A detailed account of some of the experiments will show the 
nature of the investigations, and indicate the results that have been 
obtained in so far as they bear on the subject with which we are 
here dealing. 
Experiment I. A number of hens that were laying eggs regularly 
were placed in a wooden building where they could not pick up 
substances containing lime salts, except such as were supplied with 
their food. At first they were not given any lime with their food, 
and their drink was distilled water ; in a few days they laid eggs 
with only a. membranous covering. Sulphate of lime was then 
given with the food, and in the course of a few days they commenced 
to lay eggs with the usual carbonate of lime shells. When the 
sulphate of lime was stopped, the eggs again became membranous 
and shelless. In this way it was shown that hens were able to pro- 
vide their eggs with the usual carbonate of lime shells from the 
silicate, sulphate, nitrate, phosphate, and carbonate of lime that was 
administered with their food. Further, it was found that they could 
not make use of the magnesium and strontium salts for the purpose 
of forming shells for their eggs.* It is believed that in the case of 
the various lime salts the lime passes through the blood in the form 
of phosphate to the point of secretion, where it is deposited as car- 
bonate of lime. 
Experiment II. An artificial sea water was prepared, from which 
carbonate of lime was rigidly excluded, and in this some living 
crabs were placed. They lived for many months, and after ecdysis 
produced the usual exo-skeleton of carbonate of lime from the lime 
salts, other than carbonate, present in the water, f 
* See Appendix, Table III. 
t See Irvine and Woodhead, Proc. Roy. Soc. Edin., vol. xv. p. 308, 1888. 
