Ill] 



OSMOTIC FACTORS IN GROWTH 



129 



character, that we may briefly define the species Artemia {Callao- 

 nella) Jelskii, for instance, as the Artemia of density 1000-1010 

 (NaCl), or the typical A. salina, or principalis, as the Artemia 

 of density 1018-1025, and so forth. It is a most interesting 

 fact that these Artemiae, under the protection of their semi- 

 permeable skins, are capable of living in waters not only of 

 great density, but of very varied chemical composition. The 

 natron-lakes, for instance, contain large quantities of magnesium 



Koppeniana 



160 



140 



^ 120 



100 



1000 1020 1040 1060 



Density of water 



1080 



2000 



Fig. 34. Percentage ratio of lengtli of abdomen to ceplialothorax in brine-shrimps, 

 at various salinities. (After Abonyi.) 



sulphate; and the Artemiae continue to live equally well in 

 artificial solutions where this salt, or where calcium chloride, has 

 largely taken the place of sodium chloride in the more common 

 habitat. Furthermore, such waters as those of the natron-lakes 

 are subject to very great changes of chemical composition as 

 concentration proceeds, owing to the different solubilities of the 

 constituent salts. It appears that the forms which the Artemiae 

 assume, and the changes which they undergo, are identical or 



T. G. 9 



