1894.] MICROSCOPICAL JOURNAL. 237 



white paper. It is partly from this phenomenon that 

 the crucial proof of the Protozoan nature of the diatom 

 must be drawn. During the nightly intervals for more 

 than fifteen days that I studied these evidences of an 

 animal nature, and at every time that I desired to study 

 the "melanorreha," or black flow, in the living frustules, 

 the phenomenon was always quickly exhibited if sought 

 for, and might be followed without intermission for in- 

 definite periods of study. To outline the whole range of 

 molecular vital activity in the exoplasm of the diatom, 

 and to indicate the full cycle of vital movements as seen, 

 diagramatic sketches would be requisite. But in a gen- 

 eral way the principal features may be outlined as fol- 

 lows : The living diatom (Navicula nobilis, major, viridis, 

 divergens, or any of the larger Navicular), if seen in the 

 field under the most favorable condition for study will 

 show its Siliceous case, surrounded on both sides by a 

 transparent or diaphanous zone of at least its own width 

 or a little less. Around the exterior to the parallel zones 

 is another width also equal to the width of the frustule. 

 In this outer zone there is an appearance of great oscil- 

 lating or vibrating activity in all granules used, whether 

 of India ink, indigo, Prussian blue, carmine and bacteria, 

 or any other microscopic granules that may be in the 

 liquid. This oscillating activity seems to be due to the 

 automotile power of the exoplasm itself, but at the same 

 time the Brownian movement of particles everywhere 

 else on the slide masks the interpretation of the sources 

 of movement. But, as the external or outermost layer 

 of the exoplasm has a distinct and undoubted segrega- 

 ting power over pigmentary granules, it may be safe to 

 construe the eddyings and minute whirling vortices, 

 bearing granules, as proper to the life function of the 

 exoplasmic sheath. Apart from the zones thus indicated, 

 there remains the alternating pseudopodial-flowing tis- 

 sues surrounding the opposite or terminal prows of the 



