LIVING SUBSTANCE 



27 



The Functional Relation of the Cytoplasm and Nucleus. — The 



importance of the nucleus to the cell may be shown by depriving 

 certain parts of it of its nuclear material. Thus, Hofer/ divided 

 ameba in such a manner that the nucleus came to lie in each case en- 

 tirely in one of the fragments. This particular fragment regenerated 

 very quickly into a complete cell showing a perfectly normal behavior, 

 while the non-nucleated portions lost their power of movement and 

 ingestion of food in the course of a few days and disintegrated. This 

 disintegration, however, could be prevented if at least a small frag- 

 ment of the nucleus was apportioned to these parts. 



i^^l?* 



yf 





^-^.-^ 









tm. 



Fig. 3. — The Functional Relation of the Cytoplasm and Nucleus. 

 A. An ameba divided into a nucleated and non-nucleated portion. B. The same 

 portion after an interval of eight days. (After Hofer.) 



Quite similarly, it was found that denucleated rhizopods and 

 radiolaria are able to move and to ingest nutritive particles, but that 

 the digestion of the latter is rarely completed. Furthermore, Verworn^ 

 has shown that polystomella which possesses the power of secreting 

 calcareous material, loses this function soon after its nucleus has 

 been removed. Plant cells behave in a similar way. Thus, Klebs^ 

 has proved that isolated fragments of plant protoplasm are quite 

 unable to form a cellulose membrane, while the nucleated fragments 

 retain this faculty. In addition, it might be mentioned that the 

 nucleus is situated as a rule in that area of the cell in which the most 

 active growth is taking place. This tendency is well displayed in the 

 root-hairs of plants, in which the nuclei are retained at their very tips 

 during the development of these appendages and are then made to 



^ Jen. Zeitschr. fiir Naturw., 1889. 



2 pfliiger's Archiv, 11, 1891, 1. 



3 Biol. Zentralbl., 1887. 



