198 FLORENCE A. WAITERS. 



length of the former being 21, and that of the latter 25. The 

 averages are 20.06 and 24.94 respectively. The rapid increase in 

 the number of individuals from the extremes 16.5 and 27, and 

 13.5 and 33.5 respectively is due to the larger number of indi- 

 viduals present in lot 3. 



Lot 4, Plate IV., shows the same relative conditions as those 

 found in the other lots, the mean lengths of conjugants and 

 non-conjugants being 20 and 29 respectively, while the average 

 lengths are 20.77 an d 26.65. The small number of individuals 

 occurring in lot 4 accounts for the lowness of the columns. 



Lot 5, Plate IV., is like lot 4 in the number of individuals and 

 in the shortness of the columns. There is greater irregularity 

 of outline in lot 5 than in any other of the six lots, but the mean 

 length of conjugants and non-conjugants is in accord with the 

 mean length of the other lots, the former being 22 and the latter 

 27. 



Lot 6, Plate IV., agrees with the rest in having the mean and 

 average lengths of the conjugants smaller than those of the non- 

 conjugants, the means being 23 and 32, and the averages 22.80 

 and 31.28 respectively. Thus in every one of the six lots, the 

 mean and average have been less in the case of the conjugants 

 than in that of the non-conjugants, the difference being from 5 

 to 10 units in the case of the means, and from 2 to 10 in the case 

 of the averages. From all this we should expect to find that the 

 mean and average of the total number of conjugants are less 

 than those of the total number of non-conjugants. This is the 

 case, the mean for the total number of conjugants being 21 and 

 the average 20.12; and the mean for the total number of non- 

 conjugants being 27 and 28 (or 27.5) and the average 27.67. 



One interesting fact appears in Table I. and Plates I. to IV., 

 which is shown best in Plates IV. and V., i. e., the population 

 including conjugants and non-conjugants shifts toward the left 

 or right in the various lots. Plate V. shows this for the non- 

 conjugants of lots 1,2, and 3, the means being 29, 32, and 25, and 

 the extremes 1 8 and 40, 19 and 43, and 14 and 34 respectively. 

 The means of the non-conjugants of lots 4, 5, and 6, Plate IV., are 

 29, 27, and 32 respectively while the extremes are 18 and 35, 19 

 and 34, and 17 and 40. The conjugating populations do not show 



