STRUCTURE OF PROTOPLASM OF PARAMGECIUM. 2$ 



the protoplasm inhibit it. Thus the rate of cell division increases 

 steadily with a slight elevation of temperature above the normal 

 until the critical coagulating point is reached. A lowering of 

 the temperature progressively decreases the rate of cell division, 

 until the point is reached at which it ceases altogether, and the 

 protoplasm goes into a resting condition. 



The same relation between the rate of cell division and the 

 physical state of the protoplasm is found to hold good also as a 

 result of the reactions of the protoplasm of Paramoscium to solu- 

 tions of electrolytes. 



With paramoecia from alkaline cultures, anions or liquefying 

 agents stimulate cell division, cathions and coagulating agents 

 inhibit it. Thus I have frequently observed in my experiments 

 that when the liquefying solution is too weak seriously to modify 

 the structure of the protoplasm, it will, however, greatly increase 

 the motility of the protoplasm and the rate of cell division. 

 Since the size of the paramoecia remains uniform, it follows that 

 this must indicate also increased growth and general metabolic 

 activity. In the coagulating solutions, on the contrary, there are 

 produced spherical resting cells that greatly resemble spores. 

 This antagonism between these two classes of solutions is still 



o 



more clearly shown by the fact that the anions greatly accelerate 

 the germination of spores, or the passage from a resting into a 

 motile condition. In these solutions the spherical form of the 

 spore is soon lost through a neutralization of the surface tension. 

 This has been shown in the case of some of the monads- and fresh- 

 water algae. 



R. S. Lillie l has shown that a decrease in the surface tension 

 must accompany cell division, and that this is accomplished in 

 the case of certain marine animals by the electrolytes present in 

 the sea water, for if these electrolytes be withdrawn, cell division 

 not only stops, but a partial fusion of the already formed blasto- 

 meres occurs. It appears that the surface tension relations are 

 very important in all these protoplasmic reactions to external 

 conditions. Protoplasmic movement, cell division and growth 

 all occur in opposition to the surface tension force. 2 Conse- 

 quently any external condition which neutralizes the surface ten- 



1 Lillie, BIOL. BULL., 1903, IV., p. 164. 



2 See Spaulding, BIOL. BULL., 1904, VI., p. 97. 



