NUCLEO-CYTOPLASMIC RELATION OF OXYTRICHA 3 



of R. Hertwig and his school. As a result of his work on the 

 conjugation of Infusoria, published in 1889, Hertwig has been 

 led to attach great importance to what he terms the 'Kernplas- 

 marelation.' In 1903 he discussed his theory and maintained 

 that there exists for each type of cell a definite normal volume 

 relation between nucleus and cytoplasm, and emphasized the 

 fact that the normal relation may be disturbed by various envir- 

 onmental changes. More recently he has emphasized definite 

 periodic changes of the Kernplasmarelation between successive 

 cell divisions, the immediate cause of cell division being a state 

 of cytoplasmic and nuclear tension (Kernplasma-Spannung) in- 

 duced by an overgrowth of the nucleus, and the resolving of 

 the single cell into two restores the functional Kernplasmarela- 

 tion. Hertwig interprets the large nucleus of the immature egg 

 as a sign of a state of depression, and nuclear reduction, which 

 is accomplished by the phenomenon of maturation, and fertili- 

 zation are followed by a period of rapid cell division resulting in 

 the formation of the embryo. From the study of various Pro- 

 tozoa (Actinosphaerium, Paramaecium, Dileptus) he finds that 

 senescence, 'depression' and '^physiological degeneration' are con- 

 comitant with great nuclear growth. For example, certain In- 

 fusoria, which have been supplied with a superabundance of 

 food, show^ physiological degeneration which is characterized 

 chiefly by a disproportionate development of the nucleus. A 

 return to the normal condition of the cell is brought about by a 

 direct elimination of the superfluous nuclear material, or, for ex- 

 ample, by conjugation. ''Die Befruchtung ist kein excitator- 

 ischer, sondern ein regulatorischer Vorgang." 



It is unnecessary at this time to review the many papers which 

 have recently appeared, under Hertwig 's stimulus, on the effects 

 of various internal and external conditions upon the Kernplas- 

 marelation, or its finer analysis during the various phases of cell 

 life. Popoff, for example, who has made some of the most im- 

 portant studies on the subject, found that in the infusorian Fron- 

 tonia leucas immediately after division there is a decrease in the 

 nucleus, which is followed by a slow growth (functional growth) 

 and then by a rapid growth (divisional growth) of the nucleus 



