FUNCTIONAL ACTIVITIES OF THE NUCLEUS 195 



1. The Effects of Removal of the Nucleus 



The cell which, like the erythrocyte, undergoes natural loss 

 of its nucleus may continue to exist for a considerable period, 

 and during that time actively perform function. The mammalian 

 red corpuscle, for example, according to W. Hunter, Quincke, 

 and others, exists from fifteen to thirty days. While it exists 

 we see no evidence of growth, and certainly it never propagates 

 itself. The same holds good for cells artificially deprived of 

 their nuclei ; they do not necessarily undergo immediate dis- 

 organization ; they can be the seat of certain metabolic activities. 

 According to Klebs, the enucleated cells of the alga, Spirogyra, 

 can in the sunlight produce new starch granules ; can, that is, 

 synthesize starch from the carbon, oxygen, and water absorbed, 

 the starch thus formed in the sunlight being used up in the dark ; 

 and this may continue for as long as six weeks. They may 

 further continue to exhibit motion in response to external 

 stimuli (Lacrymaria olor, Verworn) ; they may actively ingest 

 food particles. But, on the other hand, the testimony is unani- 

 mous that higher metabolic activities are incomplete. Unlike 

 nucleated portions of a vegetable cell, the enucleated is unable 

 to develop a cell wall of cellulose. Among protozoa, also, 

 Verworn has noted that enucleated pieces of foraminifera show 

 not the slightest capacity to form the internal calcareous skeleton. 

 If the enucleated cytoplasm of Thalassicola pelagica ingest 

 foreign particles, it is unable to digest them wholly, and while 

 the enucleated cytoplasm can develop a new centrosome (E. B. 

 Wilson), it cannot give rise to new nuclear material. It may 

 be laid down that if it can form new paraplasmic substances 

 like starch, it cannot form new cytoplasm and cell substance 

 proper ; that is to say, it cannot increase in bulk and undergo 

 cell division and multiplication, or, otherwise, these observations 

 conclusively prove that the nucleus is essential, not merely for the 

 vegetative activities, but also for the higher metabolic activities of 

 the cell and their due co-ordination. 



That the nucleus alone, deprived of surrounding cell substance, 

 cannot regenerate the cell is another matter. It has freely to be 

 admitted, with Verworn, Boveri, and Lillie, that there must be 

 a certain minimal quantity of cytoplasm associated with the 

 nucleus before regeneration can take place. But what this 



