DIATOM MOTION. Ill 



m}' privilege to demonstrate "■■ a.n actual protrusion of plasma 

 through the raphes at the corners of the frustule of Eunotia 

 major. The substance issuing at these points is continuous 

 with the internal protoplasm, stains like it with eosin, and 

 lies between pads of coleoderm that refuse the eosin while 

 accepting Bismark brown. To my mind it is plain enough, 

 not only that these processes are true protoplasm, but also 

 that they function in the orienting of the frustule hy rotating 

 it through i8o° of arc, as well as in locomotion. The pads 

 of coleoderm protect the protoplasm, no doubt, and the space 

 between them, just as in Piunularia, is in life invisibly filled 

 with a more fluid jelly in immediate contact with, and deeply 

 covering, this same protoplasm. All this, except the verv' 

 thin jelly, keeps its place very well on staining, differing in 

 this way from the apparently parallel arrangement in Pinnii- 

 laria, where the coleoderm masses are less consistent, and 

 collapse entirely when stained. Here, let it be well noted, is 

 an instance of external protoplasm between masses of coleo- 

 derm, a// alike invisible u'hen in operation. Moreover, the sit- 

 uation of these masses in Ennotia is far more favorable for 

 obser^-ation than the situation of a raphe stream of proto- 

 plasm in Pinnnlaria. 



And lastly, I would mention again the very important work 

 of L. Schiitt, already cited, wherein it is shown that "plasma" 

 exists and operates outside the silica, especially in the " cen- 

 trifugal thickening" of the silicious membrane, and that 

 "plasma" can be distinguished in that position from coleo- 

 derm (gallertej. 



These are some of the reasons for saying that Lauterborn 

 has not necessarily said the last word. For myself, while 

 holding no brief for the existence of external plasma streams 

 in general, I have the temerity to think him unsuccessful in 

 his^'endeavor to formulate a doctrine that will, fit with all the 

 known facts. / must think that the living stibstanee of the cell, 



*Errant Fru-tule? of Eunotia major. Proc. Acad. Nat. Sci. Phila. 1898. 



