41 8 Louise Hoyt Gregory 



The first four of the depression periods of Popoff (e.g., periods 

 4, 10, 13, 16) are merely the periodic falls in the division rate that 

 occur in the normal rhythms, and from which recovery is autono- 

 mous. Such periods are not to be confounded with the serious 

 periods of low vitality, which end in the death of all, unless some 

 external influence, such as artificial stimulation or conjugation 

 takes place. 



Calkins found in his study of Paramecium that conjugation 

 took place during the period of maturity, after a number of divi- 

 sions had been passed, and before a decrease in vitality had begun. 

 The cell at this time of maturity is recognized by a certain "mis- 

 cible" quality of the protoplasm which is characteristic of many 

 conjugating cells. This cell, however, is not a degenerate cell, 

 but a mature cell in a physiological condition such that unless it 

 is stimulated by conjugation or artificially by chemical or mechan- 

 ical means, it may degenerate and die. 



Popoff states that there is a great decrease in size during the 

 periods of low vitality. He states that the size varies from 360// 

 to 90/t, but he gives no definite data for definite periods, and no 

 data regarding the great increase in the size of the macro-nucleus, 

 or the change in the ratio between the size of the nucleus and that 

 of the cell body. 



With the view of investigating the relation of nucleus and cyto- 

 plasm to the general vitality, I have made measurements of all 

 the material which I have preserved, obtaining the length and 

 breadth of both nucleus and cell in every case. Unfortunately the 

 accurate dates of the early material were not kept, and could not 

 be used. Material was found, however, which was taken from 

 20 ten-day periods. The ratio for each individual was computed 

 and the average made from the ratios of all the individuals of that 

 period. An example may make the method more clear. One 

 of the individuals of the 26th period measured 120;^ in length 

 (=L) and 70/X in breadth ( =W), and the nucleus measured 

 45// in length (=1) and 20/< in breadth (=w). The ratio was 



120 20 



written as follows: L : W :: 1 : w = X =761 the 



70 45 



