242 STUDIES IN GENERAL PHYSIOLOGY 
water which is rich in oxygen; in other words, that we are 
dealing with a case of ‘“chemotropism.” 
XII. THE RELATION OF REGENERATION AND GROWTH IN 
TUBULARIA TO SOME OF THE INORGANIC SUBSTANCES 
CONTAINED IN THE SEA-WATER, ESPECIALLY POTASSIUM 
1. The salts dissolved in sea-water may be of importance in 
regeneration and growth, not only through their osmotic 
effect, but also through their effect upon the metabolism of 
Tubularians. We have already become acquainted with 
their osmotic effect upon regeneration and growth. We will 
now investigate whether any of the substances dissolved in 
sea-water are indispensable for regeneration and growth in 
Tubularia. In the following experiments the weight of the 
salts always refers to the dry salt after the water of crystal- 
lization has been removed. One thousand parts of sea- 
water, according to the analysis of Forchheimer, contain the 
following inorganic substances: 
Sodium chloride - 30.292 
Potassium chloride 0.779 
Magnesium chloride 3.240 
Calcium sulphate 1.605 
Magnesium sulphate 2.638 
Silicates, calcium phosphates, and residue - 0.080 
2, I added 11.3 g. of NaCl to 300c.c. of fresh water (Serino 
water) and the same amount to 300 c.c. of distilled water. 
The distilled water was thoroughly shaken in the air after the 
addition of the salt. The amount of salt in each of the 
solutions about equals that contained in ordinary sea-water. 
But while the Tubularians in a control dish of 300 e.c. of 
normal sea-water regenerated rapidly, no regeneration 
occurred in the animals of the same colony which were put 
into the pure NaCl solutions. 
I now tried 300 c.c. of each of the following solutions: 
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