The Life History of Tillina Magna 419 



coefficient or resultant. Eighteen individuals belonged to this 

 period, and the eighteen results were averaged and found to be 

 825. A curve was then made of the resultants of the twenty periods 

 obtained in a similar manner. If the nucleus (1 : w) increases in 

 size, the resultant is correspondingly raised; if the nucleus becomes 

 smaller the resultant is decreased, therefore in periods of lowered 

 vitality, when, according to Hertwig and Popoff the nucleus is 

 supposed to have increased greatly at the expense of the cytoplasm, 

 we should expect to find the resultant increased and the curve 

 varying in the opposite direction from that of the general vitality. 

 The two curves in Diagram VI show that the fluctuation of the 

 resultants vary sometimes in the same direction, and sometimes 

 :"n the opposite direction from those of the general vitality. Dur- 

 ing the periods 25-31 inclusive, the curve of the resultants is seen 

 to follow that of the division rate, and the actual measurements 

 show that when the body enlarges, the nucleus increases also in 

 size. Usually if the length of the body is longer than the average 

 the length of the nucleus has also increased, and the relationship 

 is the same. During the 26th period, one of fairly high activity, 

 in which the number of divisions per day was 1.6 (16 in ten days), 

 the average length and breadth of eighteen individuals was 132U 

 and 79/i, of the nucleus, 54/< and 25//. During a period of slightly 

 less activity, the 36th, when the division averaged 1.3 per day, 

 the average length of six individuals was 126/^, the breadth 77,^, 

 the length of the nucleus 44/i, the breadth 29/z. In this case the 

 size of both the cell and nucleus was diminished. 



Again in the 37th period, when the number of the divisions had 

 been reduced almost one-half, the average length of the cell was 

 148/i, the breadth 96/^, the length of the nucleus 40/^, the breadth 

 36/<. In this case we see that both the nuclear and the cell size 

 increased, in spite of the fact that the vitality of the protoplasm 

 was diminishing. Finally, in the 38th period, during which the 

 records show almost no division, the beef lines averaging .3 divi- 

 sions in ten days, the cell body and nucleus enlarged, the length 

 and breadth of the cell body being i83/( and 82//, and that of the 

 nucleus 56// and 45/^. The largest individual found belonged to 

 his period, measuring 200,« by 190,", and the nucleus measuring 



