510 PROCEEDINGS OF THE AMERICAN ACADEMY. 



medium. In experiments on blood corpuscles Hamburger (:02) found 

 that one C0 3 ion could, under nearly isotonic conditions, change position 

 with two chlorine ions, the corpuscles being permeable. The evidence 

 of this was the increased alkalinity of the medium, due to the substitu- 

 tion in it of alkali carbonate for alkali chloride. In the present experi- 

 ment the tests for alkalinity have fallen out negatively. An insoluble 

 carbonate of calcium may nevertheless have been formed. Perhaps also 

 an uncertain result was to be expected unless the Stentors were pre- 

 viously treated with a stronger carbon dioxide solution than their native 

 culture medium (Hamburger, :02, p. 258). Upon the other hand if the 

 Stentors changed volume, — as they would probably do even in isotonic 

 media (Hamburger, : 02, p. 259), — a correction would have to be applied 

 to the concentration of chlorine as found by chemical estimation. If the 

 Stentors swell by absorption of water, the concentration of chlorine in 

 the medium would be increased thereby. It was, however, diminished. 

 If change of volume is to account for this, we must assume a shrinkage 

 in the Stentors. Since no haematokrit determination was made, we have 

 no means of estimating this factor accurately. It remains to be found 

 out by experiment whether this operation is practicable with these 

 animals. But in the approximately isotonic solution of calcic chloride 

 used it is improbable that an important amount of swelling or shrinkage 

 occurred. The various experiments upon Stentor recorded in the course 

 of this research indicate that the animal does not readily react by a 

 change in volume to even considerable variations of osmotic pressure of 

 the physiological salts. This implies a good degree of permeability. 

 The decrease in chlorine found in the present experiment may, therefore, 

 be attributed mostly to the inward permeation of that ion, but this is 

 largely a matter of opinion. The experiments upon permeability had 

 not reached a decisive point when this work was closed, but I shall 

 continue work on this subject, and hope to publish results soon. 



X. The Extrusion of Color in Stentor. 



This phenomenon, though obscure, and bearing no known direct 

 relation to any of the preceding work, will nevertheless be described 

 briefly. In the application of reagents to Stentor it was observed that 

 in some media a mass of blue-green matter was extruded by the cell. 

 This occurred instantly upon transference to the new medium, or, in 

 some cases, after the lapse of a minute. The animal swims away leaving 

 the extruded mass or cloud behind. Occasionally the extruded mass was 

 observed to adhere to, and to be trailed along with, the moving animal. 



