PETERS. — METABOLISM AND DIVISION IN PROTOZOA. 503 



other substances stand in another class, whose activity in division I at- 

 tribute primarily and principally to their share in metabolism. The 

 manner of destruction of the cell (disintegration, for example) indicates 

 a fundamental metabolic disturbance. Moreover, such divisions as occur 

 seem to be normal. Culture experiments also show that when food is 

 abundant, that is when metabolic conditions are good, division is increased, 

 and vice versa, without anything peculiar appearing in the division process 

 itself. The absence of any perceptible modification of the normal process 

 of division, and, under given conditions, a fairly constant deviation of rate 

 of division from the normal, are evidence of a primarily metabolic influ- 

 ence of these salts. However, it is true that calcic chloride and sodic 

 chloride, for example, applied under the same conditions affect the rate 

 of division in different degrees. Numerical differences that are fairly 

 constant for a given metabolic condition of the animals result from the 

 application, for example, of calcic chloride and of sodic chloride. From 

 this fact it appears that these differences result from specific qualities of 

 the salts. It is possible, and indeed probable, that these peculiarities ex- 

 tend even to those metabolisms which underlie the process of division. 



IX. The Permeability of Stentor. 



A few experiments were made upon permeability in Stentor. In one 

 series the change in conductivity occurring in a salt medium containing 

 the animals was measured. In the other series a volumetric determina- 

 tion of the chemical change resulting under similar conditions was made. 

 I have records of eight experiments upon conductivity and of four chem- 

 ical estimations. As all the experiments of a series showed the same 

 essential results only a few examples will be described. 



Expt., Oct. 14, 1902. 



The test-cell used for the measurement of conductivity consisted of a 

 beaker, 2 cm. in diameter and 8 cm. high, a thermometer with bulb im- 

 mersed, and unplatinized electrodes 25 mm. square standing at a dis- 

 tance of 10 mm. apart in the fluid of the beaker. The latter contained 

 in both test and control experiments 5 cc. of a salt medium, the compo- 

 sition of which will be given presently. Stentors were placed in the 

 liquid in the test experiment only. The test-cell was connected in 

 parallel with the measuring tube W". The first column of the following 

 record shows the number of the observation ; the third gives the tem- 

 perature read to within 0.05° C; the fourth gives the position of the 



