1900] MICROSCOPICAL JOURNAL. 301 



note that every Navicula crossing the field or entering 

 therein would be actively engaged in picking up the mi- 

 nute wood particles, and rapidly as well as automatically 

 transporting them in any direction on its surface, trans- 

 versely back and forth, rejecting or attracting other con- 

 tiguous particles, with either a suction-like or a project- 

 ing impulse to dislodge it. Particle after parti(;le may be 

 thus picked up at the advancing end, and transferred un- 

 til a tangle of the particles becomes bunched together at 

 the rear end, where it is dislodged and drop :)ed. Should 

 one have seen this much, and have followed it for half an 

 hour or so, he would then have satisfied himself as to many 

 points, long a source of discussion and apparently miss- 

 ed entirely by writers who have studied the biological 

 characters of the diatoms through a series of years. He 

 would then be perfectly satisfied that the diatom had a 

 particularly active epidermis, with a decided muscular 

 function, in the sense of an apparent volitive power, that 

 enables its possesser to take hold by a touching contact, 

 to move the particles in a positive or negative sense, and 

 to eventually reject the load, incessantly repeating this 

 evidence of energy expended for some useful functional 

 purpose. 



Now, what has been stated above, may not appear to 

 be so wonderful to the reader, but something that cannot 

 be incidentally overlooked while the study is in progress, 

 is to the efi'ect, that while the field at the beginning is 

 uniformly strewn with the minute transparent amber- 

 colored particles of wood cells, as the diatom casually at- 

 taches a particle or particles to its body, the color of the 

 particle quickly changes to a violet shade, passing after- 

 wards to a bluish violet, and when a group of the parti- 

 cles have been massed together towards the rear end, the 

 amber color has vanished and we notice bluish and violet 

 shades, in the picked-up particles. While this change is 

 thus taking place, the mind associates the phenomenon 



