1897] MICROSCOPICAL JOURNAL 39 



gard to a differentiation of the mantle (ectoderm) envelop- 

 ing the navicular forms by the use of methyl green. I 

 had stained slides richly strewn with living diatoms up- 

 on which I made my observations and, on drying, the 

 frustules were examined superficially with condensed 

 light, and otherwise, only to find that the frustules gave 

 off the metallic sheen of the dye, with the sculptural 

 markings showing clearly; but the frustules were sur- 

 rounded where in contact with the slip by a crystalline 

 fringe of the methyl blue. They then simulated what 

 might be construed as a sort of ciliary projection. This 

 makes any deduction with reference to the mantle from 

 this mode of study an unknown quantity. The essential 

 points of C. Onderdouk's paper in relation to the mantle 

 of the diatom, and a conjecture touching the seat of the 

 vital function controlling its motile power, were adopted 

 by Wolle in his Diatomaceas of North America. Therein 

 the marvelous phenomena of the diatom's power to handle 

 and rush grains of sand, as often as its necessities may 

 require it to do so, is entirely overlooked. I allude to 

 the portion of the work upon the "Motion of Diatoms." 

 This function of the diatom to gather up and transport 

 mineral particles energetically, is one that can be readily 

 verified with the aid of a 1-6 objective. No one need 

 miss it. The study involves no difficulties. 



W. A. Terry, an expert student of the living diatom, 

 has frequently made allusions to the peculiarities of mo- 

 tion observed by himself, and from sources of supply that 

 I have never had an opportunity to inspect, he has re- 

 cently put on record the statement that some of the very 

 large living Amphiprora observed by him might pass 

 for vegetables but never for plants. As it was not his 

 object to seek for data to establish the Protozoan nature 

 of the Diatom his observations were not sufficientlycrit- 

 ical to contribute to a formulary of expression adapted to 

 animal biology. He had incidently noted that a vigorous 



