22 Livingston : Chemical stimulation of a green alga 



change in the water-content of the protoplasm. In the case of 

 solutions of high osmotic pressure, water is extracted from the 

 protoplasm directly, and it may be that this increasing density of 

 the colloidal protoplasmic solution is accompanied by changes in 

 its permeability to solute and in its general lability, and therefore 

 chemical activity, which result in a higher osmotic pressure with- 

 in the vacuole. I have been able to demonstrate this higher pres- 

 sure by the plasmolytic method in cells of the palmella form. 

 This higher osmotic pressure, as has been shown (Joe. cit., 1900), 

 will suffice to explain the change in form of the cells and their 

 partial or complete separation as they become spherical. A de- 

 crease in lability, and hence in general activity, may result in the 

 observed thickening of the wall and in a change in the manner of 

 cell-division, as is known to be the case in many plant and animal 

 tissues under the influence of dryness and low temperature, where 

 these are unquestionably concomitants of a decrease in the inten- 

 sity of vital action. 



But in case of toxic stimulation, with which this paper has to 

 deal, there is no direct extraction or witholding of water from the 

 cell, and by the principles of physics alone we are unable to see 

 any difference between the poisoned and the unpoisoned nutrient 

 medium. However, it is possible that the chemical stimulus of 

 the toxic ions may be transformed, as the disturbance of the sys- 

 tem passes within the limits of the protoplasm, and may become 

 in this way a physical disturbance. It is well known that certain 

 mineral salts hasten the coagulation of some proteids and other 

 colloidal solutions,* and it is quite reasonable to suppose that the 

 toxic ions upon entering the protoplasmic mass may produce in 

 this vital hydrosol mixture an incipient coagulation or tendency 

 toward the gel phase. If this were true it would mean that the 

 colloidal particles become aggregated to some extent into denser 

 masses, between and around which would lie a solution of less 

 density, which would contain fewer colloidal particles than before. 

 Thus, although by this supposed process of incipient coagulation 

 water is not extracted from the protoplasmic solution as a whole, 

 yet it is extracted from certain parts of this solution, namely from 



* See Whetham, W. C. D. The coagulative power of electrolytes. Phil. Mag. 

 V. 48 : 474-477- 1899. 



