102 R. A. Daly — Limeless Ocean of Pre-Cambrian Time.- 



carbonate. This effect was clue to the decomposition of cal- 

 cium sulphate by the uric acid, urea and other effete matter. 



In a second experiment it was found that in seventeen days 

 and at temperatures ranging from sixty to eighty degrees 

 Fahrenheit, the decomposition of urine mixed with sea-water 

 had precipitated practically all the sulphate of lime present. 

 A similarly complete precipitation of all the sulphate in a 

 solution of pure water and calcium sulphate present in the 

 proportion of average sea-water, was effected in eleven days 

 by the decomposition of urine added to the solution. 



In a fourth experiment, nine small crabs were placed in two 

 liters of water, where they died. Complete putrefaction set 

 in and continued at temperatures varying from seventy to 

 eighty degrees Fahr. Analysis showed that all the lime salts 

 were precipitated in the form of the carbonate. 



Irvine and Woodhead have shown conclusively that marine 

 animals, even those normally secreting limey structures, will 

 live and comparatively thrive in sea- water from which, every 

 trace of lime salts has been eliminated.* In one experiment 

 they mixed sodium chloride, magnesium chloride, magnesium 

 sulphate and potassium sulphate with pure water in about the 

 proportions of average sea-water. In this artificial sea-water 

 (No. 1) they placed a number of crabs. In their proper sea- 

 sons the exoskeletons were shed but, naturally, were never 

 rebuilt by the animals. Yet the crabs continued to feed and 

 live long after the exfoliation had taken place. 



In a second experiment '0903 per cent by weight of calcium 

 chloride was added to No. 1 water, giving No. 2 water. In 

 this the crabs lived and rebuilt their exoskeletons. This new 

 structure was composed of the carbonate and phosphate of lime 

 and chitinous matter in the proportions present in normal 

 shells. Other crabs similarly throve in a third water in which 

 the calcium sulphate in average sea- water proportion was sub- 

 stituted for the calcium chloride of No. 2 water. The proof 

 is clear that the secretion of calcareous structures is by no 

 means dependent upon the presence of calcium carbonate in 

 sea-water. 



The result of the first experiment was strikingly corrobo- 

 rated by a fourth experiment in which sodium chloride and 

 magnesium chloride were dissolved in pure water in the pro- 

 portions of average sea-water. Crabs and fish were found to 

 thrive in this water, " feeding greedily, but of course ecdysis 

 (elaboration of cast exoskeletons) in such water was impossi- 

 ble." Ecdysis was, however, carried out when calcium chloride 

 was added to the solution. 



* Proc. Eoyal Society of Edinburgh, vol. xvi, p. 324, 1889. 



