92 JOURNAL OF THE [October, 



life function of whatever protoplasmic coating that might have 

 previously given rise to the power of locomotion in the frustules. 

 It then occurred to me to test the effect of the aniline as a means 

 of differentiating the diatoms, the strong and robust, as well as 

 the hyaline forms, which are sometimes nearly lost to view in 

 balsam mounts. For this purpose I allowed a liberal amount of 

 the material to remain in a concentrated solution of aniline for a 

 period of five hours, when I washed them repeatedly in changes 

 of water until no more color was evident in the fluid removed. 

 The result of this staining has furnished me with a wide range 

 of interesting data, fairly recorded in a mount forming a part 

 of the whole series of slides made to accompany these notes. 

 Notably among the phenomena presented may be mentioned 

 that on the slide may be seen numerous large, solitary specimens 

 of Navicula viridis, and specimens of a smaller size of the same 

 grouped mostly in fours, adherent together, and others by twos 

 alone. In addition to these there are many specimens of Eunotia, 

 Fragillaria, Navicula radiosa, and other smaller forms, all showing 

 an elegant amethystine color by daylight and a reddish violet 

 by student's-lamp light, and demonstrating that the stain had 

 taken satisfactorily. This staining with aniline violet differenti- 

 ated certain structures that would not have been modified in 

 balsam mounts. The living diatoms, dried on the slide and 

 covered with balsam, present the endochrome in a uniform layer 

 of color, filling the whole internal part of the frustule, in the 

 various shades of green, olive green, or brownish hues. AVhereas, 

 with the aniline stain, the endoplasm has been rent asunder and 

 driven to the side walls of the frustule, and is there densely 

 stained and banked up against the separating walls of the quad- 

 ruple-grouped diatoms, there being a distinct hyaline or clear 

 line of silex separating the frustules where in contact, thus differ- 

 entiating separately the collapsed endoplasm of each separate 

 frustule. This action of the aniline on the larger frustules was 

 identical for all. But on the smaller forms the endochrome is 

 merely indicated by two central patches highly stained, with a 

 clear bisecting line of silica separating the two masses of endo- 

 chrome, the sides of the frustules also showing hyaline borders 

 internally. I said above that there was no appreciable thickness 

 of the layer of exoplasm on the frustules, yet it is evident, by the 



