14 LORANDE LOSS WOODRUFF 



which comparable material was available, the area of the small- 

 est cell and its nucleus, and of the largest cell and its nucleus 

 and also the area of the smallest nucleus and its cell and of the 

 largest nucleus and its cell. Table 2 gives in parallel columns for 

 each part (A, B, C and D) of the life of the race: (1) the number 

 of the ten-day period from which the specimens were taken, (2) 

 the number of specimens measured in each ten-day period, (3) 

 the range of cytoplasmic area during each ten-day period, (4) the 

 • mean of this range, (5) the range of nuclear area for each ten-day 

 period, (6) the mean of this range. A further analysis of these 

 data, in which the cells of each part {A, B, C and D) of the life 

 of the race is taken as a unit, is given in table 3. 



From these data it is clear that, on the basis of measurements 

 of area, and this is a sufficient criterion for the particular aspect 

 of the question under immediate consideration, there is great 

 variation in cell size during each period but that the mean size 

 of the cell is greatest in part A when the reproductive activity 

 is low and least in part B when the reproductivity activity is 

 highest, and then becomes larger in parts C and D as the rate of 

 reproduction gradually wanes. The data for tlte nuclear area 

 also indicate that there is great variation in nuclear size during 

 each period but that the mean size of the nucleus is greatest in 

 part A and smallest in part B, and is again larger in parts C and 

 D. The difference between the means of the cytoplasm and also 

 of the nucleus in C and D is near the limits of the probable error 

 of the determination so that it is not positively established that 

 there is a real increase in size of the nucleus and cytoplasm during 

 part D as compared with part C. It is clear, however, that the 

 mean size of the nucleus is smallest when the reproductive activ- 

 ity is greatest. It should be emphasized that the greatest dif- 

 ference in size of both cytoplasm and nucleus is seen in compar- 

 ing A and B — the periods which are characterized by the most 

 marked change in divisional activity. It is apparent then, from 

 measurements of the area of the cytoplasm and nucleus of cells 

 of this race of Oxytricha that the mean size of both the cells and 

 their nuclei is smallest at the period of greatest reproductive activity. 



