igos.j JENNINGS— HEREDITY IN PROTOZOA. 477 



under the influence of the environment was from 100.320 to 158.800 

 microns, or 58.293 per cent, of the lowest mean. The extreme 

 lengths in each line, of course, differed still more; in the D line the 

 extreme variation in length was from 104 to 256 microns, or 146.153 

 per cent, of the least length ; in the c line it was from 73.3 to 200 

 microns, or 172.851 per cent, of the minimal length. 



Effect on Breadth. — The breadth (the thickness of the body) 

 varies under different environmental conditions more readily and in 

 a higher degree than does the length. In the D line the mean 

 breadth varied in different cultures from 31.180 to 64.880 microns, 

 or by 108.08 per cent, of the lowest mean ; the extreme variation in 

 breadth, under different conditions, was from 20 to 88 microns, or 

 340 per cent, of the minimal breadth. In the c line the mean breadth 

 varied under different conditions from 23.892 to 54.160 microns, or 

 by 126.69 per cent, of the lowest mean; the extreme variation in 

 breadth was from 16 to 84 microns, or 425 per cent, of the minimal 

 breadth. The greater variability of the breadth, as compared with 

 the length is seen in the coefficients of variation of the single cultures. 

 The largest coefficient of variation for length is 15.279, while for 

 breadth it is 28.879. 



Relation of Length to Nutrition. — In general, increased nutrition 

 increases the length. But the result is not always the same, because 

 increased nutrition has two main effects : to increase directly the size 

 of the adults, and to bring about multiplication. The latter effect, of 

 course, decreases the mean length of the individuals of a culture, 

 since it induces the presence of many specimens that are young, and 

 therefore small. Increase in mean length due to added nutrition is 

 seen in Table XVIII., rows 8 to 9, 10 to 11. Decrease in mean 

 length, due to added nutrition is seen in the same table on comparing 

 rows I and 2; 3 and 4; 13 and 14; 17 and 18. This decrease is due 

 to the fact that in the nutritive fluid the animals divide before they 

 reach the length of those in the poor fluid. 



Decrease of length, due to decrease of nutrition, is seen in Table 

 XVIIL, by comparing rows 2 and 6; 7 and 8; 21 and 22; 23 and 24; 

 23 and 26. 



Relation of Breadth to Nutrition. — The relation of breadth to 

 nutrition is simpler than that of length ; in all cases increase of nutri- 



