SEA-SALTS ABOUT ARBACIA EGGS. 183 



CONCLUSIONS. 



Any attempt to standardize Arbacia egg-secretion by physical 

 methods must take into account the fact that these eggs tem- 

 porarily lower -the specific gravity of sea-water. This renders 

 unreliable any immediate application of methods depending on 

 surface tension, viscosity, or specific gravity. 



The decrease in density is accompanied by a measureable 

 chlorine deficiency in the solution and by a greater shortage of 

 total salt. We cannot attribute these effects directly or indirectly 

 to the substances which the eggs eliminate since a preliminary 

 exposure of the eggs to sea- water enables us to produce on second 

 exposure a secretion without salt-deficit. Moreover, the results 

 of total evaporation show that the salts were definitely out of the 

 solution and that there is no selective abstraction by the eggs 

 other than that dependent on the proportions in which the several 

 salts are present and their capacity for being removed by the 

 particular egg-mechanism which is involved in the process. 



This mechanism is the chorion, for eggs deprived of their jelly 

 by shaking do not cause a salt-deficit. Localization by means of 

 AgNO 3 n/io in the presence of HNO, demonstrates the concen- 

 tration of chlorides about the eggs. 



The concentration is temporary since the chorion within a few 

 hours normally undergoes disintegration in sea-water. As the 

 result of this the salts are dispersed and the specific gravity of 

 the sea-water may return to normal. A rise above normal may 

 be attributed to the presence of exudate in solution. 



In time these facts may find an application in the theory of 

 fertilization. For the present they are presented without theo- 

 retical bias although there are unavoidable suggestions in the 

 fact that the concentration of sea-salts immediately about an 

 Arbacia egg is temporarily and measurably greater than the con- 

 centration of the same salts in the surrounding sea-water. 



MARCH i, 1922. 



