NUCLEOPLASMIC RELATIONS IN ARCELLA 



19 



(fig. 18), the latter may be squeezed out very easily and in most 

 cases is free from any accompanying cytoplasm. Small lines 

 were reared from thirteen fall-sized binucleate specimens that 

 were successfully operated upon. These specimens were taken 

 from line 150.2a or 150.2b or from lines derived from them. 

 In eight of the thirteen specimens the first offspring, after the 



Fig. 18 Arcella dentata. Outline of a specimen showing where the shell was 

 broken away by means of the microdissection apparatus. The nucleus nearby 

 was squeezed out through the opening in the shell. X 207. 



operation, consisted of an empty shell and the binucleate con- 

 dition was immediately regained. Part of the data for these 

 eight cases is as follows: 



When these data are compared with those of the lines already 

 described (fig, 10 and tables 2 and 3), it will be noted that almost 

 all of the empty shells were larger and possessed more spines, 

 and the first offspring after the binucleate condition was regained 



