the Nitrogenous Matter of Plants. 113 



conclusions testify to his having made observations under un- 

 favourable conditions ; for he assumed them all to result from 

 the currents of the intracellular mucilaginous matter which 

 successively coalesced and separated from each other. But there 

 is no question that this naturalist would have given a better 

 description of them if he had persevered in the examination of 

 what he saw, varying the subject and the conditions of observa- 

 tion ; for he then might have convinced himself that most of 

 these currents take place in actually contractile canals, through 

 which the numerous granules circulate with a greater rapidity 

 than the centripetal movements of the soft matter which consti- 

 tutes them — a fact which could not take place if they were 

 transported with this matter ; moreover, he would have likewise 

 witnessed the minute granules circulate in tense and com- 

 pletely motionless canals, the contents of which received their 

 impulse from contractions remote from the communicating 

 canals. Hugo Mohl has certainly seen some of the facts that 

 I have remarked ; for he recognized the existence of minute 

 canals in the intracellular animal matter which he calls the 

 protoplasm ; and Slack, whilst denying the existence of canals in 

 certain cells, remarks on the subject of the circulation in the 

 cells of Hydrocharis morsus-rana, " The small globules follow 

 the larger ; and occasionally one of the green globules crosses 

 the cell in a current of still more minute particles, forcibly tra- 

 versing a canal which can scarcely admit them." The canals 

 which are formed in the animal azotized material of a cell do not 

 always contract themselves gradually ; it is not uncommon to see 

 several of them at a time, by a brusque movement, drive forward 

 the granular fluid that they contain. Under such circumstances 

 these canals insensibly enlarge ; and whilst the fluid that is to be 

 propelled by their contraction flows through them, they may 

 often be seen to change their relative position, and to undulate 

 like imperfectly stretched cords until they acquire an increased 

 rigidity and an enlarged capacity; then they become out- 

 stretched, assume a dull-white hue, and contract once or oftener 

 in succession. After these contractions have occurred, the 

 partially emptied canals, more elongated than formerly, occa- 

 sionally reunite in a bundle, fixed on one hand to the extremity 

 of the cell, and on the other hand to the nucleus — a bundle 

 which then simulates a mucilaginous-like axis without distinction 

 of parts. However, if the observation be pursued, after half-an- 

 hour or sometimes more, according to conditions which I have 

 found it impossible to appreciate distinctly, these same canals 

 fill themselves afresh and resume their contractility. Such is the 

 mechanism by the aid of which the granular fluid contained 

 Ann. $ Mag. N. Hist. Ser. 3. Vol x. 9 



