490 PROCEEDINGS OF THE AMERICAN ACADEMY. 



diminishes from the hyperisotonic towards the isotonic region, the two 

 limbs of the curve show by their rise an approach to normal conditions. 

 In other words, all concentration curves of a single physiological salt have 

 the characteristic median elevation with depression towards either extreme. 

 We are compelled to admit that the physico-chemical phenomena 

 involved in the interaction of cells and media, while yielding some results 

 in the attempt at analysis, are still very obscure. However, if we begin 

 analysis with the larger and more evident complexes of phenomena (in 

 Roux's sense), we can treat them from another standpoint, that of adjust- 

 ment. But the description of the phenomena can never be complete 

 without an account of the physico-chemical processes, which are, to say 

 the least, one form of the expression of the life of the organism. 



The Adjustments of Stentor. 



As my experiments in the treatment of Stentor with salts increased in 

 number, certain apparent inconsistencies, as well as certain constant rela- 

 tions, attracted my attention. There is insufficient detail in the data 

 thus far obtained to explain these conditions by physico-chemical methods. 

 This fact led me, not to the abandonment of physico-chemical explana- 

 tion, but to consider the phenomena from another point of view also. 

 This has to do with the adjustment of the animal to different conditions. 



Before drawing conclusions upon adjustment from the preceding data 

 and the curves partially representing them, it is important to estimate 

 their range of applicability. Are the mean results above recorded, fixed 

 values? I do not maintain that in their absolute, numerical value they 

 are even approximately invariable. Occasionally repetitions with solu- 

 tions of previously used concentrations gave results surprisingly close to 

 the first ones ; but in other cases there was much deviation. Further 

 observation showed this variation in results corresponded to the conditions 

 of the adtures from which the animals originated. As I was engaged 

 throughout this research in the management of cultures as my source of 

 material, I had favorable opportunities to become familiar with newly 

 established, with flourishing, and with declining cultures. Experiment 

 convinced me of the great importance of knowing the origin of the 

 Stentors used. Results vary in their numerical value with the vitality, 

 i. e. the physiological condition, of the animals. A Stentor culture as it 

 passes through its successive stages offers excellent examples of this 

 variation. In general I selected as the source of my material only 

 healthy cultures. Perhaps the best criterion of this condition was the 

 longevity of the culture. It is to be especially observed that the curves 



