358 PROCEEDINGS OF THE SOCIETY. 



ment. This was typically exhibited by species of Navicula, FinnuJaria, 

 Surirella, etc., and was undoubtedly a very wonderful phenomenon for 

 which no quite sufficient cause had yet been demonstrated. The 

 evidence, however, seemed to indicate that it would eventually be 

 proved to be essentially a primitive protoplasmic movement, due prob- 

 ably to the flowing of somewhat sticky protoplasm along a groove open 

 to the exterior and usually situated in the raphe. At any rate, some- 

 thing which could adhere to particles of debris certainly moved back- 

 wards and forwards along the raphe, or along the keels in the case of 

 Surirella, and it was difficult to imagine what this could be unless it 

 were protoplasm. Several exhibits included motile Diatoms in addition 

 to the principal object shown. 



There was next the Oscillatorian type of movement, that snake-like, 

 creeping, gliding, bending, rotating movement exhibited by species of 

 Oscillatoria and allied genera, of which some specimens were being shown 

 that evening, and also by such bacterial forms as Beggiatoa. It was, 

 perhaps, the most mysterious of all the types of movements exhibited 

 by microscopic organisms, and nothing approaching a satisfactory ex- 

 planation had yet been given of it in spite of various hypotheses and 

 many positive assertions as to the presence of cilia, etc. 



The movements of Desmids, too, while in some ways resembling 

 those of Diatoms and Oscillatoria, although much slower, appeared to 

 have peculiarities of their own which entitled them to be considered as 

 belonging to a distinct type — the Desmidian type, as it might be called. 

 In some cases it was probably due to the exudation of mucilage, but 

 this scarcely seemed sufficient to account for the remarkable way in 

 which Desmids would extricate themselves from a confused mass of 

 sediment and gather together on its surface. There were several 

 exhibits that evening showing various species of Desmids, but the time 

 available was probably too short to allow of a demonstration of their 

 movements. 



Leaving these somewhat obscure types of movement, they had next 

 to consider the very definite type of flagellate movement. A flagellum 

 was the source of locomotion in a very large number of minute micro- 

 scopic forms, both vegetable and animal, and, without much doubt, the 

 movement was due essentially to a rapid series of waves or bends of 

 greater or smaller magnitude running along the flagellum. It had been 

 thought that the motion of a flagellum was of a spiral or corkscrew type, 

 but this was certainly not true in all cases. Ulehla had shown that the 

 light-space produced, under high-power dark-ground illumination, by a 

 "flagellum in motion was of very varied form, often curved or bent, 

 usually broader in one view than in the other, and that sometimes it 

 was even at right angles to the line of progression of the organism. 

 These facts were clearly incompatible with the idea of a spiral action, 

 although not with that of a series of waves running continuously along 

 the flagellum. Much work, however, was required to demonstrate the 

 true action in individual cases. Apparently no flagellate organisms 

 were being shown that evening. 



Passing on to ciliary movement, it was to be noticed that in this type 

 they had to deal with co-ordinated movement of a large number of 



