PETERS. — METABOLISM AND DIVISION IN PROTOZOA. 511 



No evident injury resulted to the Stentor either immediately or remotely. 

 The animal later divided in media that had produced this effect. How- 

 ever, those media which were found most favorable to the organism did 

 not produce extrusion, although these media contained a proportion of 

 certain substances which alone would have produced it. The effect 

 seemed to be inhibited by other substances present, which were never 

 observed to produce extrusion. Observation showed that the rejected 

 matter might originate from any part of the surface of the Stentor, its 

 boundary frequently forming a line parallel to the outline of the animal. 

 The growth of this envelope in thickness could easily be observed. The 

 extruded matter varied somewhat in consistency and depth of color. At 

 times it was scarcely visible, and seemed to disappear in the surrounding 

 water. In other eases it was a heavy deep-green mass. It always 

 showed a more or less gelatinous consistency, so that it could be shaken 

 as a whole by jarring the watch-glass containing it. Its nature and mode 

 of production made it a difficult object to examine. I was unable to 

 discover any structure in it, and I think it was a homogeneous mass. 



The close analogy of this phenomenon with extrusion of coloring 

 matter from blood corpuscles was evident. It led to the suggestion that 

 there might be here a relation to osmotic conditions similar to that shown 

 by the process of " laking" in blood. Had this been true, the same use 

 as in the latter case might have been made of Stentor cells to arrive at 

 an approximate estimation of the osmotic concentration of their medium. 

 However, the results of tests which entirely disprove this view of the 

 phenomenon are given in the following table. The first column gives 

 the number of the experiment, the second indicates the substance, and 

 the third gives the extremes of concentration in molecular parts at which 

 and between which extrusion was observed, — E signifying that extrusion 

 occurred, that none was observed. A parenthesis encloses the nearest 

 concentration at which non-extrusion was observed. The original record 

 contains observations at many intermediate concentrations, but these are 

 not given in the table. 



Range molecular parts. 



.155-.001 (.0001) 

 .1-.001 (.0001) 

 .0G-.0006 (.0001 ?) 

 •2-.001 (.0001) 

 .2-.001 (.0001) 



