NUCLEOPLASMIC RELATIONS IN ARCELLA 37 



d. Relations between nuclear number and diameter within small 

 families and between fa7nilies 



The nuclei were counted in only a few of the specimens at 

 this time, but it was soon discovered that their number varied 

 in the members of a single family, and that one branch of a 

 family might consist of specimens with a certain number of nuclei 

 and another branch of the same family of specimens with a 

 different number. Thus in family 11 there was one branch 

 with 5 nuclei and another with 6; in family 26, one with 7 and 

 another with 8; in family 30, one with 6 and another with 7, 

 and in family 12, one with 4 and another with 6. 



It was also noticed that the specimens belonging to a branch 

 containing the lesser number of nuclei tended to be smaller 



-30 



Fig. 31 Arcella polypora. Pedigree of part of the specimens in family 22 

 showing large variations in diameter. The unit of measurement is 4.3 /u. 



than those belonging to another branch of the same family 

 with more nuclei. However, the members of a branch of one 

 family with a certain number of nuclei, differed in their diameter 

 from the members of branches of other families with the same 

 number of nuclei. For example, in family 11 the measurements 

 of the nine specimens in the 5-nucleated branch were as fol- 

 lows: 31, 30, 30, 29, 29, 28, 28, 28, 28, whereas in family 6 

 the five specimens in the 5-nucleated branch measured 23, 24, 

 25, 25, and 26 units. 



Table 10 gives the distribution of diameters and the mean 

 diameters of thirteen families. The numbers in each family 

 are small, but it seems probable that the different families 

 differ constitutionally in diameter. This appears particularly 

 when families 6 and 7 are contrasted with families 8, 11, 12, 



