DIATOM MOTION. I05 



cause to effect. This filament, he considered, was the equiva- 

 lent of the gelatinous threads by the protrusion of which cer- 

 tain desmids force themselves along. In place of Prof. 

 Smith's jet of water we are offered a jet of jelly. 



Meantime, O. Miiller had made minute study of the sili- 

 cious parts of naviculoid diatoms, at least of the raphe and 

 its terminal pores. He had postulated currents of " plasma " 

 issuing from the cell at the end pores, running along the sur- 

 face at the raphe, and reentering the cell at the central 

 nodule. He attributed the motion of the diatom to the reac- 

 tion between its immediate environment and these external 

 streams of protoplasm. In opposition to Biitschli, he opined 

 that the so-called filament was rather a hindrance than a help, 

 in so far as it was prone to stick to the substratum, and had 

 to be pulled loose or broken off. At first, indeed, he doubted 

 the general existence of such a filament, and thought it a 

 mere evanescent result of a temporary stoppage of the reen- 

 tering plasma current, causing a piling up of plasma at the 

 central nodule. At this point Lauterborn entered into the 

 discussion with vivacity, finding the external protoplasmic 

 currents of Miiller to be "entirely hypothetical:" and the 

 progress of the controversy, from this on to its comparatively 

 peaceful close, is given at length in Lauterborn 's elaborate 

 work already cited as appearing in 1896. 



Lauterborn 's actual contribution to the subject was of a 

 nature to make an impression. It is bound up with his 

 researches on the contents of the diatom cell and on the con- 

 struction of the silicious envelope. His work on the cell- 

 contents is of great importance, and he added to our know- 

 ledge of the details of the silicious pairts of Phuudaria and 

 Surirella. The raphe of the former had already been demon- 

 strated to be a real cleft, but Lauterborn traced its actual con- 

 struction almost from end to end, and gave elaborate illustra- 

 tio^ns of its cross-sections. For Surirella he showed finally 

 and beyond the possibility of further cavil the rifts in the 

 keels. The moving Surirella had always given every evidence 



