NUCLEOPLASMIC RELATIONS IN ARCELLA 77 



semipermeable, allowing a constant, but selected flow of mate- 

 rials from the nucleus into the cytoplasm and vice versa. In- 

 volved in the theory is also the idea expressed by Sachs in 1892, 

 and the following year by Strassburger in a slightly different 

 form. According to Sachs, the nucleus and that part of the 

 cytoplasm that falls within its 'sphere of influence' make a 

 morphological and physiological unit. He proposed the term 

 'energid' for such a unit, and this term might well be employed 

 in describing conditions in Arcella, since, as we have seen, the 

 nuclei in both the binucleate and multinucleate species are 

 approximately equidistant from one another, as though each 

 were acting as the dynamic center of an equal portion of the 

 cytoplasm. Strasburger ('93) recognized a limit to the distance 

 through which the metabolic interchange between nucleus and 

 cytoplasm could take place, and was able to show that in the 

 cells of certain plants the ratio between nuclear size and cell 

 size was fairly constant. He accounted for cell division on the 

 hypothesis that when the cytoplasm had increased so as to 

 extend beyond the working sphere of the nucleus the normal 

 ratio was regained by the division of both nucleus and cyto- 

 plasm into two. The nucleocytoplasmic-relation theory as we 

 now know it is largely due to the investigations carried on by 

 Richard Hertwig and his students. Hertwig ('03) came to 

 the conclusion that in every cell under normal conditions there 

 is a definite relation between the quantity of cytoplasmic and 

 nuclear materials, which he called the 'Kernplasmarelation.' 

 In favor of this theory is the discovery by Gerassimoff ('02) 

 that in Spirogyra if nuclei are segregated in one cell following 

 cell division this binucleate cell becomes larger than the normal 

 uninucleate cells; and the generalization of Boveri ('02, '05) 

 arrived at from studies of the cells of sea-urchin larvae, that 

 ''Die Grosse der Larvenzellen ist eine Funktion der in ihnen 

 enthaltenen Chromatinmenge, und zwar ist das Zellvolumen 

 der Chromosomenzahl direkt proportional." According to 

 Hertwig, the magnitude of the K/P (nucleus/cytoplasm) ratio 

 determines vital processes such as growth, division, senescence, 

 and physiological degeneration. The latter, for example, result 



