PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 345 



mella) or the slime by which the animals adhere to the substratum 

 (Amceba, Difflngia, Polystomelld). Beside these results should be 

 placed the well-known fact that dissevered nerve-fibres in the higher 

 animals are only regenerated from that end which remains in con- 

 nection with the nerve-cell, while the remaining portion invariably 

 degenerates. 



^ 



A 



D 



Fig. 161. Formation of membranes by protoplasmic fragments of plasmolyzed cells. [TOWN- 

 SEND.] 



A. Plasmolyzed cell, leaf-hair of Cucurbita, showing protoplasmic balls connected by strands. 



B. Calyx-hair of Gaillardla ; nucleated fragment with membrane, non-nucleated one naked. 



C. Root-hair of Marchantia ; all the fragments, connected by protoplasmic strands, have formed 

 membranes. D. Leaf-hair of Cucurbita; non-nucleated fragment, with membrane, connected 

 with nucleated fragment of adjoining cell. 



These beautiful observations prove that destructive metabolism, as 

 manifested by coordinated forms of protoplasmic contractility, may 

 go on for some time undisturbed in a mass of cytoplasm deprived of 

 a nucleus. On the other hand, the building up of new chemical or 

 morphological products by the cytoplasm is only initiated in the 

 presence of a nucleus and soon ceases in its absence. These facts 

 form a complete demonstration that the nucleus plays an essential 



