196 ON VARIABILITY AND ADAPTATION 



proves is not that the nucleus is not the dominating portion of 

 the cell complex, but only that the association of nucleus and 

 cytoplasm is essential for full cell activity. By the lack of per- 

 ception of this distinction it may be noted that Verworn's treat- 

 ment of the whole subject of cell processes is greatly weakened 

 if not vitiated. His facts prove that nucleus and cytoplasm 

 are equally essential for the full function of the cell, not that 

 they are of equal value. We may as well argue that in the 

 community of bees the individual drone or worker is of importance 

 equal to the queen, because we find that the queen-bee, if separ- 

 ated from the rest of the community, is incapable of obtaining 

 food for herself, and so starves to death. I shall refer later to 

 what I regard as the right conception of the relationship between 

 cytoplasm and nucleus. 



2. Gross Changes in the Nucleus during Activity 



Among these may be noted, (1) alteration in the position 

 of the nucleus in cases in which there are indications of localized 

 as distinct from diffuse cell activities, and (2) alteration in size 

 and shape of the nucleus accompanying active function. 



In the animal organism possessing cells with a body which 

 is small in proportion to the size of the nucleus, examples of 

 the first order would appear to be rare, though they are not 

 entirely wanting. Thus Korschelt has shown that in the egg 

 rays of the water scorpion (Nepa), with their cells having remark- 

 able nuclei, long branches from two adjoining nuclei send out 

 processes which come into close proximity. In the space between 

 these a chitinous deposit gradually shows itself, and when the 

 mass of chitin is fully formed the processes are withdrawn. In 

 the plant, movement of the nucleus towards the area of new 

 formation in the cell is relatively common ; thus when there is 

 the active formation of a thick cell membrane along one aspect 

 of the cell, it has been noted that the nucleus becomes eccentric 

 and approximated to the region of new development. There 

 is a similar eccentric localization of the nucleus during the 

 development of root hairs (Haberlandt). I need but mention 

 instances of the second, namely, of alteration in size — they are 

 now so well known. The earliest observations were those of 

 Heidenhain years ago upon the different appearance of the nuclei 



