118 PROCEEDINGS OF THE ACADEMY OF [1898. 



certain deeply stained lines are seen in immediate contact with the 

 silica of the ventral surface, and running down from the pseudo- 

 nodule and the end nodule. These dark lines follow the course of 

 the channels in the silica shown by the photographs, and would be 

 explained by the existence of richly protoplasmic fluid. In a single 

 case one of these lines was seen to issue, to all appearance, through 

 the raphe and enter the coleoderm. 



The above results of observation and experiment would seem to 

 me to be conclusive proof that Eunotia major, and by inference 

 other nearly related species and genera of the Fragilariece, move 

 by the action of organs that may be called coleopodia. This con- 

 clusion, however, is far from touching the question of the means of 

 locomotion in Pinnularia and its allies, and I have endeavored to 

 indicate some of the differences of the phenomena to be explained 

 in the two cases. It may be added in this connection that while a 

 large Pinnularia in rapid motion not infrequently gives evidence of 

 brisk iuternal currents such as O. Miiller has described, such cur- 

 rents have not been observed by me in moving Eunotia. Under 

 rather high powers one only sees, near the corners of the frustule, 

 in the vicinity of the raphe, a certain internal commotion among 

 the very small protoplasmic granules, a spasmodic movement back 

 and forth, a weaving about. This movement differs alike from the 

 streaming of cyclosis and the Brownian trembling, and it is trace- 

 able with difficulty, if at all, far from the corners. Nevertheless, 

 the channelling of the frustule is of a character to indicate the exist- 

 ence of currents, and further observation may yet reveal them. 



EXPLANATION OF PLATES. 

 Plate vi. diagrammatic. 



Fig. 1. — Representation of Eunotia major moving across a piece of 

 mica and revolving it in the opposite direction. 



Fig. 2. — A frustule, valve view, in A resting upon its dorsal girdle, 

 B revolving, and C reaching its normal motile position and 

 moving in the direction of the arrow. 



Fig. 3. — A short filament showing stages in the development of the 

 coleopodia, and a free motile cell with development com- 

 plete. Stained with Bismarck brown and eosin. 



Fig. 4. — Valve view of motile cell, stained with Bismarck brown 

 and eosin. 



Fig. 5. — Stained cells, including a group of two. 



