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 - . 080 



2. I added 11.3 g. of NaCl to SOOc.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 c.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: 



