196 



FLORENCE A. WAITERS. 



to throw a projection of each one upon the drawing table below. 

 A permanent record of each one was obtained by drawing a line 

 perpendicular to the long axis at each end. The figures given 

 are the measurements of the projections rather than of the 

 individuals themselves and are 192 times the actual size. Thus 

 in the table: 



the size of the projection rather than the actual size is given. 

 Translated, these figures would be: 



But since it is the relative length rather than the absolute length 

 which is of importance in this case, it has not seemed necessary 

 to divide all the numbers given below by 192, and the figures 

 denoting the size of the projection stand in the statistics which 

 follow. For the sake of overcoming any element of personal 

 error which may have entered into the measurements, all meas- 

 urements falling half way between one mm. mark and the next 

 are considered with those .5 mm. larger. 



The results obtained by careful measurements of six lots of 

 Blepharisma undulans are in accord with the results obtained by 

 Pearl ('07) and Jennings ('n), i. e., in Blepharisma undulans (i) 

 the mean length of the conjugants is less than the mean length of 

 the non-conjugants, (2) the variation in length is much less among 

 the conjugants than among the non-conjugants, and (3) the 

 correlation in size between the two members of a pair is distinctly 

 marked, the larger mating with the larger and the smaller with 

 the smaller. To take up first the difference in length between 

 the conjugants and non-conjugants: Table I. shows that in all 

 six lots the mean length of the conjugants is less than that of the 

 non-conjugants. 1 Plate I. shows that the mean length of the 



1 The ordinates indicate the size of the individuals while the abscissas indicate 

 the number of individuals; thus the position of the column indicates the size while 

 the height of the column indicates the number of individuals. 



