Size in Relation to Multiplication Rate 97 



generating capacity. Popoff ('08) in Frontonia, and 

 Calkins ('Ha) and Young ('22) in Uronychia found 

 that larger percentages of individuals survived if cut 

 at times other than during the process of fission. But 

 such differences can be definitely correlated with differ- 

 ences in the physical state of bodily materials. In fact 

 the size of minimal reorganization masses depends 

 far more upon the time required to form a new sur- 

 face layer on cytoplasm or on nucleus than upon the 

 amount of material required for other functional proc- 

 esses. This is perhaps best shown by the large dif- 

 ference in the result whether cutting is done slowly or 

 rapidly, whether over a large surface or a small, 

 whether all at one time or in successive portions. 



Genetic factors. The readiness of formation of new 

 body surfaces varies among different clones of a single 

 species. This was particularly noted in Paramecium 

 caudatum by Calkins ('lib). It is probable that it 

 also varies with cultural conditions. 



Chemical factors. But the largest factor in the vel- 

 ocity of formation of new protoplasmic surfaces ap- 

 pears to be the chemical conditions which prevail. This 

 was long ago appreciated by Kiihne ('64) as a result 

 of his experiments in placing Amebse in various solu- 

 tions of salts. Recently Mast ('26, '28), Chambers 

 ('26), and Reznikoff ('28) have begun to discover the 

 role of particular ions in particular concentrations up- 

 on the viscous, cohering, and imbibing properties of 

 the cytoplasm of Ameba. In Stentor, Heilbrunn ('27) 

 noted the particular role of calcium ions in determin- 

 ing the rapidity with which new surfaces are formed 

 when cytoplasm is squeezed from the body. Similar 

 tremendous variations in speed of "surface precipita- 

 tion" in response to crushing in calcium salt solutions 

 can be found in Ameba, Paramecium, and undoubtedly 

 many other species of unicellular organisms. 



