12 THE GENEEAL CHARACTERS OF CELLS, BY S. STRICKER. 



granules that are imbedded in the protoplasm, or from the 

 occurrence of certain changes in the form of the protoplasm 

 itself. The movement of the granules in this case is a passive 

 movement. The granules which have been introduced from 

 without, as well as those which have developed in the inte- 

 rior, providing they are not too heavy, move as the result of 

 the action of the forces we are about to consider. 



The movement of the granules is either continuous or 

 vibratory. 



The continuous movement, again, presents two forms ; first, 

 a relatively slow progression, corresponding to and following 

 the changes of form of the cell. 



Engelmann* states particularly he has observed, in the 

 corpuscles of the cornea, that they begin to move in order, 

 from before, backwards, and refers to similar observations of 

 Hofmeister on the Plasmodia of the Myxomycetse. 



Secondly, There is a swifter flowing movement that far 

 exceeds the changes of form of the protoplasm in rapidity. 



Max Schultze describes the movement of the granules in the 

 threads of sarcode that the Foraminifera project through the 

 apertures of the shell, as a gliding or streaming motion of 

 granules imbedded in a sarcodal substance .f "As the pas- 

 sengers in a broad street swarm together, so do the granules in 

 one of the broader threads make their way by one another, 

 oftentimes stopping and hesitating, yet always pursuing a 

 determinate direction, corresponding to the long axis of the 

 thread. They frequently become stationary in the middle of 

 their course, and then turn round ; but the greater number pass 

 to the extreme end of the thread, and then reverse the direc- 

 tion of their movement." It cannot be doubted that these 

 continuous motions depend on vital processes in the cells. At 

 all events, we are acquainted with no analogous phenomena in 

 unorganised bodies. 



The vibratory movement of the granules calls to mind the 

 so-called molecular movement of Brown. It may be witnessed 

 in the salivary corpuscles, and under certain conditions in the 



* Ueber die Hornhaut. Leipzig 1 , 1867. 

 t Das Protoplasm d. Rhizopoden, p. 11. 



