32 A. \V. GREELEY. 



The protoplasm of paramoecia from an alkaline culture is lique- 

 fied by temperatures between 23 C. and 30 C., by anions, and 

 at the cathode during the passage of the constant current. The 

 paramoecia also react positively to all these chemical and physi- 

 cal conditions. The protoplasm of the same paramoecia is 

 coagulated by temperatures below 20 C. and above 30 C., by 

 cathions, and at the anode during the passage of the current. 

 The organisms are negative to all these conditions. The struc- 

 tural changes produced by electrolytes are partially reversed in 

 paramoecia from a slightly acid culture, and the reactions of the 

 organisms are also partially reversed to the electric current, com- 

 pletely so to solutions of electrolytes. In every case the reaction 

 of a Paramcecium to an external stimulus leads it to remain 

 under those conditions which liquefy the protoplasm. Attrac- 

 tion is accompanied by liquefaction, repulsion by coagulation. 

 As far as the physical structure of the protoplasm is concerned, 

 the conclusion from these facts seems to be that the protoplasmic 

 particles are physically identical with colloidal particles. Hence 

 the protoplasm of Paramceciuin is essentially a colloidal solu- 

 tion whose particles carry a definite charge of electricity. The 

 sign of this charge appears to depend on certain external chemi- 

 cal conditions, of which the alkalinky of the surrounding medium 

 may be taken as one of the most important. The sign of this 

 charge is seen to determine not only the structural modifications 

 of the protoplasm, but also the reactions of the paramcecia to 

 chemical and electrical stimuli. This conception of the physical 

 structure of protoplasm is also used to explain the effect of 

 external conditions on the processes of cell division, growth 

 and movement through the operation of the laws of surface 

 tension. 



ZOOLOGICAL LABORATORY, 



WASHINGTON UNIVERSITY. 

 February 10, 1904. 



