Size of Nucleus 175 



tion which might be temporarily shoved aside by sup- 

 posing that assimilation automatically proceeded as 

 fast as ingestion could be accomplished. 



Growth. The real test of the hypothesis was to see 

 how the nucleus grew as compared with the body dur- 

 ing the life of the individual. This study was under- 

 taken by Popoff ('08) upon the large ciliate Frontonia. 

 Individuals which were growing at 25°C. and at 14°C. 

 were killed at various intervals of time after they had 

 emerged from fission. The relative sizes of the nuclei 

 of these single individuals are plotted in figure 56, 

 while the sizes of their bodies are represented earlier 

 in figure 13. The bodies were relatively larger than 

 the nuclei at all ages up until shortly before fission, 

 when the nuclei underwent great enlargement. 



This was a surprisingly good fit to the theory. Pop- 

 off ('09) proceeded in the same way with Parame- 

 cium (figure 57), and with only fifteen individuals to 

 measure from, arrived at the identical result. 



The agreement of Popoff's results with a theory 

 announced five years earlier must have been so con- 

 vincing as to deter other investigators from studying 

 the rate of growth of nuclei. But, now twenty years 

 after, it would be interesting to see how the measure- 

 ments result when made by an investigator who had 

 no theory upon the subject. Examination of Popoff's 

 linear measurements show that an error of one scale 

 division in the values here and there would have made 

 large differences in the outcome. In other words, at 

 each time interval enough determinations are required 

 so that they can be treated statistically. 



Multinucleate species. Another way of testing 

 whether nuclear bulk was proportionate to size of body 

 was to study species having variable numbers of nuclei 

 (more than one). Such a species was the heliozoan 

 Actinosphaerium which Hertwig ('98) had previously 



