VELTEN—KUPFFER—SCHWALBE 165 



of the vegetable cell. More plainly than by Heitzmann 

 there is shown in Velten's communication the influence 

 upon the Vienna biologists of the work published by Briicke 

 in 1861, in which is set forth the necessity of an organisa- 

 tion in the protoplasm, i.e. of its being made up of more 

 solid and more fluid parts. Velten found the living pro- 

 toplasmic strands, which traverse the cell sap (more particu- 

 larly in Cucurhita pepo), to be frequently of a finely fibrillar 

 structure, the spaces between the fibrillae showing the same 

 low power of refraction as the cell sap. His interpretation 

 of his observations is as follows. The protoplasm is made 

 up of a system of fine canals filled with watery fluid, which 

 are quite shut off from the cell sap, and traversed frequently 

 by " transverse partitions." The conflguration of the chambers 

 so formed is " constantly altered by the movement of the 

 protoplasmic walls." The granules of the protoplasm are 

 to be found in or on the walls, not in the, intervening 

 fluid. It may happen, however, under abnormal conditions, 

 that granules get into the latter, where they then exhibit 

 lively molecular movements. Velten pointed out particu- 

 larly that this canal system of the protoplasm, was in no way 

 to be confused with " a spongy framework." While in 

 1873 he believes he has observed these structural relations 

 only in cells subjected for some length of time to weak 

 induction-currents, in 1876, when he also gives a figure, 

 this is no longer definitely stated. His statements as well 

 as the figure given in 1876 prove quite definitely that Velten 

 really had observed the fibrillar structure of the living and 

 streaming protoplasmic strands, and had also seen plainly 

 the net-like connections of the fibrillse. It appears, however, 

 natural and beyond all doubt, that he could only have 

 seen distinctly a few strands and threads of the meshwork, 

 and has therefore made the width of the meshes much too 

 great — a fact which, as remarked already, is equally true of 

 the older observations. / 



Kupffer observed in 1874 the reticular structure of the 

 protoplasm quite plainly in the salivary glands of Periplaneta 

 orientalis, both in the fresh condition and after treatment 

 with the most various reagents. Since the width of the 



