NUCLEOPLASMTC RELATIONS IN ARCELLA 



45 



involved a decrease or increase of only one nucleus, but they 

 were nevertheless easily observed and very constant. Some 

 of these are indicated in table 16. 



6. Results of a further increase in nuclear number. Period 4- 

 On June 17, 1918, specimens were transferred to the laboratory 

 at Cold Spring Harbor, Long Island. They were not affected 

 by the change of food thus made necessary, and continued to 

 divide about every two days. Two principal problems wer^e 

 attacked during this period: 1) an attempt was made to obtain 

 specimens in family 5 with more than 6 and less than 3 nuclei, 

 and, 2) new families were reared (from wild specimens brought 



TABLE 16 



Arcella polypora. Famihj ap. 5. Table shoiving the difference in diameter of 

 parent and offspring at the time of changes in the number of nuclei. The unit of 

 measurement is 4-3 ix 



from Baltimore) with the object of determining what differences 

 exist between different families with respect to nuclear number 

 and the diameter of the shell. 



Speci7nens in family 5 with 7 nuclei. Table 17 gives the 

 correlation between the number of nuclei and the diameter 

 of the shell of ninety-two specimens that were reared at Cold 

 Spring Harbor from June 17 to July 27, 1918. Here again as 

 in those reared at Baltimore (table 15) there is a high correla- 

 tion between these two characters. The mean diameter in 

 each class differs somewhat from that of the corresponding 

 class obtained at Baltimore, but this is probably due to the 

 small number of specimens involved. In both tables (15 and 17) 

 the mean diameter increases as the nuclear number increases. 



