328 Proceedings of Royal Society of Edinburgh. [sess. 
were separated and placed in large clear glass jars filled with the 
same No. 1 water, in which a continuous current of aerated No. 1 
water was kept circulating, and provided with flint (acid-washed) 
gravel, stones free from lime, and growing sea-weed. They were 
fed regularly with raw mussel flesh. 
Some of the jars were placed in sunlight so that the water might 
he slightly warmed (and oxygenated), and others were kept in the 
dark and as cool as possible ; notwithstanding the greatest care, 
however, the results were of a negative character so far as successful 
new shell formation was concerned. Indeed, the experiments up 
to this point failed entirely. 
On reference to the first portion of our paper on this subject, it 
will he found that we hazarded the opinion that there might he 
inter-action between the chloride of sodium and lime salts present 
in sea water, and possibly “ production of chloride of calcium, 
which might then be almost directly assimilated by animals, and 
secreted as carbonate of lime. Following out this idea we added to 
a portion of the No. 1 water chloride of calcium, equivalent in 
amount to the lime already present as sulphate in the No. 1 water. 
This water is referred to in the Appendix as ‘No. 2, Artificial 
Sea Water.’ ” Three shore crabs, weighing from 300 to 400 grains 
each, were introduced into this water in glass jars provided with 
growing sea-weed and acid-washed gravel, through which a constant 
current of No. 2 water was also circulated. On the 29th of July 
one of these animals cast, leaving a perfect envelope (or shell) con- 
sisting of carbonate of lime and chitinous matter which had formed 
the exo-skeleton (see Appendix) ; its body then presented the soft 
pulpy appearance common to this condition of the animal. It con- 
tinued in this state for two or three days, during which period it 
was very shy and was unable to feed, but gradually the animal, 
which had, meanwhile, increased in size very considerably, began to 
lose its flaccid appearance and to gain substance, so much so, that 
in four or five days the sac-like bag or covering which now occupied 
the position of the shed carapace, and which was a soft pliable 
membrane entirely free from calcareous matter, was hardening, and 
within ten days there was sufficient calcareous matter deposited on 
the animal to allow of its resuming its regular functions. The 
deposition began first and continued with greatest energy upon 
