CHANGES OF FORM IN CELLS. 23 



the addition of water : hyaline processes are thrust out, in the 

 interior of which a streaming motion of granules can be dis- 

 cerned, so that the form of the cell undergoes a change. At 

 other times the processes are again withdrawn, or undergo 

 repeated alterations of form after they have remained pro- 

 truded for a short period. Ecker* regarded these phenomena 

 as indications of spontaneous movement, but If have shown 

 that the movements of these cells, when no water has been 

 added, are of quite a different kind, and that the above occur 

 only on the addition of that fluid. 



The streaming movements of the granules contained in the 

 pseudopodia of the marine rhizopods is also arrested by distilled 

 water. J The greater number of amoeboid cells become globular 

 when exposed to the action of water, but after a few seconds 

 a vibratory movement of the granules is observable, after which 

 the cells generally burst ; some, however, remain globular for 

 a time, and then recommence their amoeboid movements : this 

 is particularly the case if, as has already been mentioned, they 

 are moistened with a one-half per cent, solution of common 

 salt. 



The cells that assume a globular form on the addition of 

 water, seem also to increase in size, from which it may be con- 

 cluded that they imbibe some of the fluid. 



The laws by which water or a solution of any substance is 

 thus taken up are unknown. It seems probable, however, that 

 diffusion plays a part in the process. 



We may also conceive that the water which has penetrated 

 into the interior of the contractile substances acts as a stimulus, 

 because we are already acquainted with the similar action 

 exerted by water on muscular tissue, and because electrical 

 currents produce similar effects on the cells. 



The statement made by Hermann, that the spherical condition 

 assumed by the cells in water or other dilute medium is a state of 

 rest, is certainly plausible. The circumstance that they will remain 



* Icones Physiol. 



t Ueber die Selbstandige Bewegung, Wiener Sitzungsberichte, 1864. 



| Max Schultze's Archiv, Band ii. 



