46 



ROBERT W. HEGNER 



Of particular interest are the thirty-two specimens in table 17 

 in the 7-nucleated class. These were all derived from a single 

 progenitor with 7 nuclei. The parent of this progenitor had 4 

 nuclei and gave rise to three other progeny, two of which pos- 

 sessed 4 nuclei and the third, 6. Among the progeny of the 

 7-nucleated specimens were 4 with 6 nuclei and one with 5. 

 The greater mean diameter of the 7-nucleated specimens may 

 be accounted for by the presence of one more nucleus than in 

 the specimens previously studied. 



TABLE 17 



Arcella polypora. Family ap. 5. Correlation table for nuclear number and 

 diameter of shell of ninety-two specimens reared at Cold Spring Harbor. The 

 unit of measurement is 4-3 m- Coefficient of correlation, 0.818 =>= 0.023 



7. Uninucleate and binucleate s-pecimens obtained by cutting 

 experiments. Since no specimens were found with only one 

 or two nuclei, cutting experiments w^ere resorted to to obtain 

 them. These experiments were carried on in the same way as 

 those performed earlier on A. dentata and described in part 2 

 of this paper. Ten specimens were operated on in this series 

 of experiments. These specimens possessed 3, 4, or 5 nuclei, 

 and were cut in two so that the pieces contained 1, 2, or 3 nuclei 

 each (fig. 34) . From these pieces nine lines were obtained. 

 Some of the data derived from these lines are indicated in table 



