54 



THE AMERICAK MONTHLY 



[March, 



to Mr. Cox's supposition are insuper- 

 able, irrespectively of the visible evi- 

 dence obtainable from broken-up spe- 

 cimens which I have been in the habit 

 of studying ever since I began to 

 write on the diatoms some five-and- 

 twenty years ago. 



If the cellules are closed at both 

 their extremities during the life of the 

 organism, each individual cellule must 

 be full either of protoplasm or some 

 other more or less fluid substance, 

 unless, indeed, each contains a gas, 

 or constitutes a perfect vacuum, which 

 is scarcely within the bounds of pos- 

 sibility. If each chamber contains 

 protoplasm, it is obvious that the re- 

 mains of this, during the preparation 

 and mounting of the specimen, would 

 be recognizable amongst the larger 

 species, either by the employment of 

 optical or chemical tests — that is to 

 say, during the boiling in acid, or 

 burning on mica, the fluid contents 

 would burst the films, and in many 

 cases leave behind the evidence of 

 their former condition. Now, in my 

 experience, such evidence has ever 

 been forthcoming, and, judging from 

 what is known of cellular structure 

 - in organic life generally, whether ani- 

 mal or vegetable, there are no ex- 

 amples of truly vacuous cavities, inas- 

 much as all organic tissues whatever 

 are pervious to dialytic or osmotic 

 action. 



It is no doubt true that the organic 

 silica of the diatom, perfectly hyaline 

 as it looks, is in reality a ' colloid,' 

 and hence, as it contams an infinitesi- 

 mal percentage of water, just as flint 

 itself does, dialytic action may take 

 place through the film under notice. 



But even then the perviousness to 

 moisture of the diatom, if it really 

 keeps the chamberlets full of fluid 

 during the vitality of the organism, 

 would not suffice to settle the present 

 question ; for, if any fluid whatever 

 remained in the little cellules, should 

 the specimens have been but recently 

 taken from their element, it would 

 burst the film on the application of 

 heat, and inevitably burst the walls, 



whilst traces of the disruption would 

 occasionally be visible under the mi- 

 croscope. Again, if the chamberlets 

 contained gas of any kind, and in 

 spite of the effects of the boiling in 

 acids, this gas were too minute in 

 quantity to burst the walls, we should 

 certainly be able to detect gas bubbles 

 in some of the chamberlets. But, as 

 is well know, the bubbles so common 

 in mounted specimens are not due to 

 the cellules having originally con- 

 tained gaseous material, but to the 

 accidental admission of air during 

 mounting. 



The only remaining alternative is 

 that the cellules cannot be considered 

 closed cavities, and hence that the 

 alleged presence of an external invest- 

 ing and closing film is illusory — a 

 fact of which I have never yet had 

 reason to entertain a doubt. 



G. C. Wallich, M. D. 



London, Jan. 35. 



The Working Session of the Ameri- 

 can Society of Microscopists. 



The Executive Committee of the 

 American Society of Microscopists 

 having placed in my hands the work 

 of organizing the Working Session at 

 the meeting of the Society to be held 

 in Cleveland, Ohio, next August, I 

 have prepared the following scheme 

 of work for demonstration at that 

 session, which, though far from be- 

 ing as complete as could be desired, 

 is submitted as approximating the 

 maximum of work that can be suc- 

 cessfully elaborated and demonstrated 

 in the limited time of the working 

 session — one-half day. 



SCHEDULE OF WORK. 



1 . The use of the micro-spectro- 

 scope and its application to original 

 lesearch. 



2. The use of the polariscope in 

 original research. 



3. Micro-photography and its ap- 

 plications as an aid to research. 



4. The use of the camera lucida, 

 various styles and methods. 



