DIATOM MOTION. I07 



acute angle with the surface. of the valve. This is the 

 Biitschli-Lauterborn filament. These things take place on 

 the forward end of each valve during locomotion. When the 

 diatom reverses its direction, the forward end now becoming 

 the rear end, the same phenomena are seen on the other ends 

 of the same valves, all the streaming being in the reverse 

 direction. 



Thus there would appear to be a stream of adhesive sub- 

 stance over the raphe, bound on each side by coleoderm, and 

 a protrusion of a sticky filament at the place where this 

 stream ends. The stream over the raphe is deep, even to half 

 the width of the cell, and the ink particles do not penetrate 

 it. Lauterborn views this stream and the filament which is 

 an outflow from it as thin coleoderm (gallerte) and would def- 

 initely account for the motion of the diatom as being the 

 result of the friction of the raphe-stream and the pushing of 

 the filament upon the diatom's surroundings. 



Miiller, in taking up the question at this point, welcomes 

 the raphe-stream as a special case of his "purely hypothe- 

 tical " plasma currents upon the surface of the valve. Laut- 

 erborn responds that none of the current is plasma, since it is 

 absolutely invisible in water all the way down to the raphe, 

 and under no circumstances shows the characteristic, proto- 

 plasmic, webby structure, a structure visible in the most ten- 

 uous rhizopod extensions. Moreover, the filament, which is 

 constantly being shed, is of the same character, and it is 

 inconsistent with all we know of the economy of cell life for 

 an organism thus to be rejecting living substance. But coleo- 

 derm does not move itself? True enough. Lauterborn 's 

 view is, that the raphe stream and the filament are alike the 

 outcome of a rapid secretion of jelly over the whole surface of 

 the internal protoplasm, most voluminous where the bulk of 

 protoplasm is largest, issuing through the forward pore, along 

 th^ raphe, and with special force at the central nodule, where 

 the largest mass of all is located. Spirting out here under 

 heavy pressure, just where Miiller had placed the reentering 



