542 EDMUND NEWTON HARVEY 



and other alkaloids, KCN and lack of oxygen (Budgett '98) and 

 has been designated as cytolysis. An excellent account of the 

 process is given by Wulzen ('09). 



The essential effect is a change in shape, with the protrusion 

 of clear drops (vesicles) from the surface and the separation of a 

 more or less well defined membrane. On account of the change 

 in shape (shortening and widening) it is difficult to say how much 

 swelling accompanies cytolysis. 



The exact changes vary somewhat according to the alkali and 

 the strain of Paramoecium used, but the sequence is fairly con- 

 stant, as follows: — 



Motor reflex or avoiding reaction. 



Change in shape. 



Swim backward (not always observed). 



Color change appears (with NH4OH). 



Swim slowly in circles without making headway. 



Clear drops appear at surface. 



Swimming ceases. 



Drops fuse to a membrane.^ 



Surface bursts. 



Color change appears (with NaOH). 



At a certain point the power of swimming is lost and at another 

 point the red is changed to yellow and diffuses out of the cell. 

 The relative times for these two events to take place is given in 

 table 6. 



One drop of stained Paramoecia was mixed with 10 cc. of the 

 alkaline solution in Syracuse watch glasses. A glass plate 



^ 'Membrane' is used in rather a broad sense. The type of membrane depends 

 on the Paramoecium and on the alkali used. In Ca(0H)2 the clear drops extruded 

 rarely fuse and no definite membrane forms. In Ba(0H)2 or NaOH an irregular 

 membrane may form but I have never observed cilia beating on it. In NH4OH 

 a very definite membrane is lifted off, which must be the original surface film 

 of the animal for the cilia may be seen beating on it. The original surface of 

 Paramoecium within the membrane lifted off (in NaOH) is often perfectly clear 

 and distinct and trichocysts may be seen beneath it. Lifting off of the whole 

 ectoplasm plus pellicle by the accumulation of liquid beneatli, occurs also in 

 NaOH. Where this does not take place we must regard the membrane formed 

 as either the pellicle or a haptogen film on the surface of the clear drops. The 

 fact that this film is impermeable for NaOH points to the former alternative. 



