1888 - 89 .] Mr Irvine & Dr Woodhead on Carbonate of Lime. 327 
and sea water, by which means we might obtain results more in 
keeping with the statement we had originally made. 
Dr John Murray placed all the resources of the Marine Station 
at Granton at our disposal, at the same time defraying the cost of 
the analyst, whose duty it was to watch the progress of the experi- 
ments and to perform the analyses which appear in the Appendix 
to this paper. 
§ 2. Our first object was to obtain artificial sea water free from 
carbonate of lime, and this we obtained by adding to fresh water 
the salts present in sea water (in proportion shown in Dittmar’s 
analyses in the “Challenger” chemical report), carefully excluding 
all trace of carbonate of lime. The composition of this water 
appears in Appendix under Table II. (“Artificial Sea Water, 
No. 1 ”). 
On analysis we found that the fresh water employed contained 
2-68 grains of lime salts (principally as carbonate) per imperial 
gallon. Hydrochloric acid was added (previous to the addition of 
the salts) in quantity more than sufficient to decompose any 
carbonate of lime originally present in the water. The resulting 
artificial sea water No. 1 (see Appendix), which had a specific 
gravity of D026, was allowed to settle in tanks, and was then aerated 
by means of spray jets of a mixture of air and this water, sent into 
the tanks at a high pressure by the pumping engine attached to the 
Marine Station. This aerated water was neutral. 
We collected a number of male and female common shore and 
edible crabs, choosing these animals as being handy and most 
likely to meet the general requirements of our experiments, and 
placed them in this water No. 1, giving them raw mussel flesh for 
food. Whether it was in consequence of the change from their 
ordinary food, or whether it was owing to the absence of vegetable 
and animal organisms in the water, or wdiatever may have been the 
reason, they did not thrive (except upon one another). 
During the early months of summer many beautiful examples 
of exfoliation occurred, but in this water we never had a case where 
the animal could replace the calcareous exo-skeleton it had thrown 
off ; and ultimately the undefended animal was sure to become a 
prey to one or other of his fellow captives. 
With a view to watch their movements more carefully, they 
