I04 PALMER : 



valve, and traced a current of indigo particles from the front 

 end of the moving frustule, along the raphe to the forward 

 pore of the central nodule. At this point the minute par- 

 ticles collected into a little ball which rotated rapidly, as if 

 acted upon by a jet of water issuing from the pore. Having 

 reached a certain size, the balls broke up and lengthened into 

 a filament, moving off to the rear at an acute angle with the 

 surface of the valve. Immediately thereafter a second ball 

 began to form at the same place, and the whole process 

 repeated itself continuously. All this is best observed when 

 the diatom is lying on its girdle. The action confines itself 

 to the forward half of each valve. When the diatom reverses 

 its direction of motion, the same phenomena are observable 

 in the other half of each valve, the motion of indigo particles 

 being in the reverse direction. So far as appears, Prof. 

 Smith did not draw any final conclusions as to mechanism 

 beyond the suggestion of jets of water issuing from the for- 

 ward pore of the central nodule. Nevertheless his work, 

 though finding notice mainly in apologetic footnotes of subse- 

 quent authors, was the starting-point of later investigations 

 of much interest. His observations have been ampl}^ con- 

 firmed, except only the existence of rapidly rotating balls ; 

 and in this matter I also must confess ray failure to see such 

 in moving Pi)nmla?ia, including Navintia dadyhis, N. major, 

 etc., after following them for long periods of time in ink 

 emulsion. Lauterborn's account of what goes on at the ante- 

 rior pore of the central nodule seems to me more nearl}^ correct. 

 Biitschli, and his brilliant student, R. Lauterborn, also 

 worked with Piyinularia, using India ink to outline the invi- 

 sible coleoderm, and finding that a stream of particles of ink, 

 traveling from the forward end to the central nodule, pushed 

 out finally to form a gelatinous filament. This filament 

 changed its direction of growth when the diatom changed its 

 course, moving always in opposition. Biitschli therefore 

 announced that without much doubt this backward expansion 

 of the jelly filament stood to the motion of the diatom as 



