56 PHYSIOLOGY OF STREAMING MOVEMENTS 



pulsate, and that non-nucleated fragments of Amoebae obtained by artificial 

 fission may continue to exhibit amoeboid and streaming movements as soon 

 as the shock of the operation has passed away. Similarly, ciliary move- 

 ments may continue in non-nucleated fragments of columnar epithelial 

 cells, of swarm-spores, and of ciliate Infusoria 1 . Fischer has shown that 

 the cilia of Bacteria possess a similar power of independent locomotion, 

 while Hofmeister, Pfeffer, Hauptfleisch, and Gerasimoff have all found 

 that streaming may continue in non-nucleated fragments of cells of both 

 Phanerogams and Cryptogams 2 . 



In all the experiments carried out upon protoplasts covered by a cell- 

 wall, the possibility of the existence of fine plasmatic connexions between 

 the nucleated and non-nucleated portions of the cell has been overlooked. 

 That this is by no means a negligible possibility is shown by the fact that 

 Palla 3 concluded, in opposition to the previously accepted view 4 , that a 

 renewed formation of the cell-wall was possible around both nucleated and 

 non-nucleated fragments of protoplasm. Tow-nsend 5 has, however, since 

 shown that Palla overlooked the existence of fine plasmatic threads con- 

 necting the nucleated and non-nucleated fragments, and that in the absence 

 of these threads no power of forming a new wall is possessed by the latter. 

 Hence it seemed quite possible that the same explanation might apply 

 to the continuance of streaming movements in non-nucleated fragments in 

 Phanerogamic cells. 



There are several methods of obtaining completely isolated non- 

 nucleated cytoplasms, and if these remaia uncovered by a cell-wall, we 

 have a double security against error. Cells containing protoplasts frag- 

 mented by plasmolysis or by induction shocks may be opened and the 

 contents allowed to escape in an isosmotic solution of sugar. Streaming 

 may often not recommence, but in many cases it may be shown by 

 non-nucleated fragments for a few hours or even days afterwards ( Val- 

 lisneria, Elodea, Tradescantia, Trianea). In intact cells the protoplasmic 

 connexions may be broken or destroyed by the localized application of 

 strong induction currents 6 . If the thread is not as yet covered by 

 cellulose, it breaks and is retracted, but streaming may continue apparently 

 unaffected in successful experiments, although it always ceases sooner in 

 non-nucleated fragments than in nucleated ones. Pollen-tubes (Narcissus^ 

 Lilium) often exhibit a natural process of fragmentation when grown on 

 gelatine or in certain fluid media, and streaming movements may occa- 



1 Hertwig, Zelle, 1893, p. 264 ; Verworn, Allgem. Physiologic, 1895. 



2 Fischer, Bacteria (Clar. Press), 1900; Hofmeister, 1. c., p. 52 ; Pfeffer, Zur Kenntniss d. Plasma- 

 haut u. d. Vacuolen, 1890, p. 279; Hauptfleisch, Jahrb. f. wiss. Bot., 1892, Bd. xxiv, p. 172; 

 Gerasimoff, Ueber die kernlosen Zellen bei einigen Conjugaten, 1892, 1896. 



z Flora, 1890, p. 314. 



4 Klebs, Bot. Unters. a. d. Bot. Inst. zu Tubingen, 1888, Bd. n, p. 552. 



5 Jahrb. f. wiss. Bot., 1897, Vol. XXX, p. 484. 6 Townsend, 1. c., p. 484. 



