1905.] Effects of Alkalies, etc., on Eggs of Echinus. 107 



normal solutions in distilled water were prepared. The carbonates and mono- 

 sodic phosphate were made up in decimolecular strength, and the di-sodic 

 phosphate in Y V molecular strength, on account of its lower solubility. A 

 saturated solution of calcium hydrate was prepared in distilled water 

 decanted from the lime, and standardized against decinormal acid, and this 

 standardized solution was used in small measured amounts for addition to 

 the sea-water containing the samples of eggs as in the other cases. 

 Similarly, in the case of the carbonic acid, a comparatively strong solution of 

 carbonic acid was prepared by passing the gas through sea- water ; this solution 

 was standardized at once with decinormal alkali, using phenol-phthalein as 

 indicator, and immediately added in appropriate small measured quantities to 

 the various measured sea- water and egg-mixtures. 



It may be pointed out that there was no appreciable variations in osmotic 

 pressure of the sea-water caused by the addition of the reagent solutions, 

 because the volume added was small in comparison with the volume of sea- 

 water and egg-mixture to which it was added ; further the decinormal solu- 

 tions added, though hypotonic, do not lie very far below the molecular 

 concentration of the sea-water. If the decinormal solutions had been 

 made in sea-water instead of distilled water, an equal or greater amount of 

 change in osmotic pressure would have resulted on account of their being 

 hypertonic, and also precipitation of constituents of the sea-water would in 

 certain cases have occurred. The change in osmotic pressure was, however, 

 in all cases quite a negligible quantity. 



The experiments involved the use of a large number of vessels on account 

 of the long series of mixtures of sea-water and fertilized eggs with their 

 varying amounts of added chemicals of different kinds, and we had no 4 "- 

 anticipated this heavy demand when starting upon our expedition. Hence, 

 we had to make use of such materials as we could find in the Marine 

 Biological Station, or obtain at Port Erin. The earlier experiments were 

 made in well washed out glass jam-pots such as are used for collecting fresh 

 marine specimens, but later we found ordinary plain tumblers of the usual 

 size most convenient. 



The amount of surface for aeration compared to the volume of fluid was the 

 same in each case throughout each series of experiments, and henee the 

 results obtained are strictly comparable with one another. 



The method of procedure in starting an experiment was as follows : — The 

 shells of a number of Echini were cut open circularly so as to expose the 

 uninjured gonads, until a ripe male and a ripe female had been obtained as 

 shown by examining under the microscope, and ascertaining that the 

 spermatozoa were active, and the eggs of mature size and well formed. 



