PROTOPLASM OF PROTOZOA 61 



HYDROSTATIC PRESSURE 



High hydrostatic pressure (500 atmospheres) causes collapse of 

 pseudopodia, and a rounding up o( A. proteus (Brown and Marsland, 

 1936). This effect is apparently the result of liquefaction of the plasma- 

 gel, an effect which inhibits the normal sol-gel transformation. However, 

 similar high hydrostatic pressures seemed to have little or no effect on the 

 beating of flagella or cilia of other Protozoa (Marsland, 1939). 



THE EFFECTS OF ELECTRIC CURRENT 



The effects of electric current on many Protozoa have been studied 

 (see Hahnert, 1932, for literature). 



Bayliss (1920) has shown that on passage of an electric current of 

 the proper intensity through Amoeba, immediate gelation of the proto- 

 plasm takes place and all Brownian movement stops. As the Amoeba re- 

 covers, the protoplasm solates and the particles again take up their active 

 motion. Strong electric shocks caused irreversible coagulation. More re- 

 cently Luce (1926), Mast (1931b), and Hahnert (1932) have studied 

 the effects of electric current on Amoeba. In general, as stated by Hah- 

 nert, a constant electric current provokes responses in Amoeba by defi- 

 nite polar actions at the ends of the organism. Destruction or solation 

 of the plasmagel occurs at the cathode end immediately, then contractive, 

 and later, disintegrative processes occur at the anodal end. These re- 

 sponses are directly dependent upon the strength of the current. 



IRREVERSIBLE COAGULATION 



Acids and certain salts, such as mercuric chloride, in the proper con- 

 centrations, cause irreversible coagulation of protoplasm. Protozoa are 

 therefore often "fixed" in such solutions for morphological studies. The 

 causes of the irreversible coagulation which occurs at "normal" death 

 are obscure. 



Surface Properties 



A discussion of the physical properties of the surface layer in Protozoa 

 involves its structure, which has been analyzed by a study of its gross 

 morphology, elasticity, contractility, extensibility, viscosity, and ultra- 

 microscopic architecture. It is obvious that any conception of the physi- 

 cal structure of the surface membrane must be in harmony with its 



