igos.] JENNINGS— HEREDITY IN PROTOZOA. 435 



lots together (Table XXXIV.) we have io6 specimens at this age 

 (row 15, Table X.) ; the mean length is 143.82 microns, the mean 

 breadth 50.832 microns, while the mean ratio of length to breadth is 

 35438 per cent. 



The polygon for variation in length at this age is shown at c, 

 Diagram 4, p. 440. 



(/) Age 25 to 45 Minutes {Table XXXV.). — From the same lot 

 6 (Table X.) from which came the first sets aged o to 19 and 18 to 

 28 minutes, there were taken on the same day 25 specimens that were 

 allowed to reach the age of 35 to 45 minutes (row 9, Table X.). 

 Growth has now become much slower. These specimens average 

 17 minutes older than the last set, yet they have increased in length 

 only about 6.5 microns. The breadth remains about the same; the 

 slight increase shown in the figures is probably not significant, since 

 it disappears at the next stage. The mean ratio of breadth to length 

 continues to decrease, reaching now 37.296 per cent. The correla- 

 tion between length and breadth is more strongly positive than before 

 (.2799), indicating that these dimensions are not changing so decid- 

 edly in opposite ways. 



The polygon for variation in length at this age is shown at d, 

 Diagram 4. 



(g) Age yf, to go Minutes {Table XXXVI.) . — Forty-two speci- 

 mens of this age were measured, taken on the same day from the 

 same lot from which came the sets last described (lot 6, Table X.). 

 The specimens average about twice the age of those in the last set, 

 the absolute increase being 45 minutes, yet the growth in length has 

 been only about 12 microns, which is about the same as the growth 

 in the first five minutes after separation. The breadth still remains 

 about the same; it is notably less than in the very earliest stages. 

 The ratio of breadth to length continues to decrease, reaching now 

 33.558 per cent. Meanwhile the correlation between length and 

 breadth has increased greatly, till now, at .5232, it is not much below 

 that of the culture as a whole (.6469). 



{h) Age to po Minutes. — From a single culture of D, on a 

 single day, we have thus measured 140 young specimens, varying in 

 age from o to 90 minutes. The constants for variability and corre- 

 lation of such a collection are of interest ; thev are therefore given 



