1894.] MICROSCOPICAL JOURNAL. 207 



another time, I prepared a slide covered with a coating 

 of very fine black pepper dust, with the object of noting 

 the behavior of the living Naviculse while in contact 

 with the pepper. I observed that all of the diatoms 

 previously alive, were inactive and apparently killed by 

 the acrid or pungent principle of the pepper. From 

 what has preceded, it is readily observed, that a large 

 portion of the activity of the diatoms, while travelling 

 on the slide, in the field of view, is passed in a ceaseless 

 labor of moving around, catching up, whirling and drop- 

 ping sand grains, and other minute particles. 



Returning once more to the so-called " oil globules" 

 in the various species of Naviculae, etc. ; while I stated 

 that I had made a close stud}" of their motile phases, I 

 did not attempt to follow their morphological changes 

 further than that ; but from Prof. Smith's researches, I 

 noted that he had followed species of Naviculae through 

 a complete life cycle, and that he observed that the mo- 

 tile globular masses coalesced and united together in the 

 frustule, where they finally appeared as two large 

 rounded masses, which were termed "the fully differ- 

 entiated endoplasm," which give origin to the sporan- 

 gial frustules derived from the conjugation of two con- 

 tiguous frustules, or in like manner, of a single frustule 

 performing the same function within the limits of its 

 own frustule. 



In my studies, as recorded herein, of the large Navic- 

 ulae, Surirellae, and Nitzschiae, I made use of a magnifica- 

 tion of 300, 600 and 1,200 diameters, which latter case 

 gave me by comparative estimate, floating images of the 

 diatoms nine and twelve inches in length, and, in the 

 case of Nitzschia scalaris, eighteen inches ; but the gen- 

 eral study was made with a power of 600 diametes, 

 agreeing approximately with the dimensions of the spe- 

 cies found in Schmidt's, Atlas and Wolle's Diatomaceae of 

 North America. 



