6 Prof. H. Karsten on some Phenomena of 



The circulation then proceeds for several hours, becoming weaker 

 and weaker, until it at length entirely ceases, the fibres of the 

 cloudy fluid growing more obscure, from an apparent coalescence 

 within the interior of the cell. 



The central nuclear cell, moreover, usually sank, daring these 

 phenomena, lower down in the cell ; and the same organ, when 

 attached to the wall, often showed also a slight change of place. 



The largest portion of the upper extremity of the cell is 

 usually divided, by only one obliquely directed stratum of circu- 

 lating fluid, into two long sections; but its lower portion is 

 broken up into several rounded clear spaces by shorter layers. 

 In the interspaces formed by the contiguous borders of three 

 such clear spaces, as also in the canals running along the wall 

 of the cell, bounded by the adjoining sides of other two, circu- 

 late more rapidly the usually thicker, filiform and more visible 

 threads. 



Hence it is evident that the internal cavity of the thick- walled 

 large hair-cell is subdivided into several hollow spaces, filled 

 with a transparent homogeneous fluid, and that these spaces are 

 capable of undergoing some change of form very gradually, and 

 are separated from one another and from the external wall, more 

 or less completely, by means of a system of mucous currents. 



There also exist within the interior of the hair-cell, betwixt 

 the spaces filled with homogeneous watery fluid, other spots 

 unoccupied by the turbid matter in circulation; or such are 

 seen to originate under the eye of the observer by a disintegra- 

 tion of the circulating substance. At such spots the larger 

 clear spaces are therefore separated by very thin dissepiments. 

 All these conditions bear testimony to the fact that the hair-cells 

 of Urtica urens, and, in fact, many parenchymatose plant-cells, 

 are occupied, at a certain stage of their development, by a tissue 

 composed partly of non-nuclear cells (secretion-cells) which are 

 separated from one another not by a firm but by a fluid inter- 

 cellular substance. When such a hair-cell is moistened with water, 

 imbibition takes place through the external wall, and the inter- 

 cellular matter gets difi'used, the more remote portions becoming 

 intermingled with the more central. The process may be watched 

 for hours, and the streams seen to set out, until at length the 

 delicate diosmotic and, doubtless, assimilating membrane of the 

 endogenous cell-wall becomes destroyed by the excessive im- 

 bibition of the water. 



From this object, therefore, the physiologist might satisfy his 

 problem of explaining the vital phenomena of the organism from 

 its structure and from the physical and chemical changes taking 

 place in it, without being compelled to have recourse to an in- 

 herent contractility not referable to these factors. The rotation 



