494 PROCEEDINGS OF THE AMERICAN ACADEMY. 



circumstance, of taking results for comparative purposes after an approx- 

 imately forty-eight-hour interval. 



Evidently this is a medium to which Stentors are well adjusted. But 

 the addition of salt-containing food, for example hay or leaf extract, gave 

 a mass-culture that was a failure. Possibly such an addition brought 

 about a disturbance of the salt balance, the existence of which will be 

 established by experiments described further on in this section. In- 

 spection of the radicals represented by the salts of this medium shows a 

 duplication between different salts that will render it unnecessarily diffi- 

 cult to determine their separate shares of activity by the method of 

 excluding one salt after another. A more favorable opportunity to do 

 this would be afforded by a salt medium in which duplication of radicals 

 had been avoided, provided the physiological necessities of the animal 

 should be compatible with it. For several reasons it seemed to me much 

 better to begin with single salts and proceed step by step to the more 

 complex combinations. Hence each experiment of the following series 

 is based upon the more or less tentative conclusions drawn from those 

 which precede it. General and conclusive results can be shown only 

 trom the series as a whole. 



Expt., Jan. 8, 1903. 



The Stentors used in this experiment were lighter in color than hardy 

 Stentors, and were somewhat undersized. Of the chemical conditions in 

 the combination Na 2 HP0 4 -f CaCl 2 , it is for our purpose necessary to 

 know only that all the ions, or radicals, used are represented in the solu- 

 tion. CaHP0 4 is soluble in dilute solution and still more so in the 

 presence of some other salts, for example NaCl (Dammer, '94, Band II. 

 Theil 2, p. 320). 



Media. hr. 1 da 2 da. 4 da. 



.00050 m. Na 2 HP0 4 50 50 50 50 



.00050 m. CaCl 2 60 62 64 64 



.00025 m. Na 2 HP0 4 \ 



and .... 50 52 48 45 

 .00025 m. CaCL J 



.00025 m. Ca20H 50 30 33 31 



.00050 m. Ca20H 50 



.00050 m. HC1 50 



