PHYSIOLOGICAL RELATIONS OF NUCLEUS AND CYTOPLASM 345 



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

 {^Amoeba, Difflugia, Polystomella). 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. 



\ J 





A 



C 



U 



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 Gaillardia ; 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 Cumrbita ; 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 



