IO THE STRUCTURE AND LIFE 



^y- 



,.0 "If viewed on the girdle 



face (fig. 5) a ball is seen 

 to form in the centre of 



-/"> I each valve at a and a', and 



c *" "'N^ it is remarkable that each 



**X- 5- of these small spheres spin 



round on its axis just as if a small jet of water was being whirled over 



it from a small opening situated at the central apex of the median line 



at the point c of figure 6. 



" When the balls have attained a certain volume they suddenly burst, 

 and the particles of indigo move off, following the direction of e and c 

 (fig. 5). Immediately after the rupture of the ball, a new one commences to 

 form in the same place. The particles follow the directions e, c (fig. 5), 

 while the diatom itself moves in the opposite direction indicated by the 

 arrow d. If the movement of the diatom be reversed, the particles of 

 indigo follow a path opposite to that shewn in the figure. I have observed 

 this curious phenomenon for hours together, and I can assure you that 

 it is a glorious spectacle. I had in the field of the microscope some 

 magnificent specimens of large Finnuiaria, and the phenomenon showed 

 itself very distinctly when the free movement of the frustule was arrested 



by a grain of sand or other 

 , obstacle. The colour used 

 by me was an ordinary water 

 colour, indigo blue paint, 

 s ' sufficient being used to make 



the water fairly dark. Another observation which I made at the same 

 time established to my mind the existence of a hyaline gelatinous envelope, 

 external to the frustule, which prevented the particles of indigo coming in 

 contact with the silicious part. When the diatom moved, it pushed before it 

 string of indigo particles which always remained at the same distance 

 from the front portion of the frustule, as is indicated in figure 6 d, and 

 which was pushed out of the way during the movements of the diatom. 



" A very slight application of red aniline (fuchsine) proved decisively 

 the existence of this gelatinous and usually invisible envelope, for it coloured 

 it distinctly, even before the tint had appeared in the field of the microscope. 

 The aniline always instantly stopped all movement of the diatoms with 

 which it came into contact." 



Mr. Otto Midler also has for a long time carefully studied the movement 

 of diatoms. We are convinced that we can give no better idea of the 

 opinions of Mr. Muller than by translating a short resume which our 



