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®n tbe Cultivation of "©iatome b^ artificial 



flDeane* 



By Dr. P. Miquel. (Translated from La Diatotniste.) 



Chapter III. 

 CULTURE OF DIATOMS UNDER THE MICROSCOPE. 



WHx\T I have already said respecting the ordinary cultiva- 

 tion of Diatoms will admit of my being very brief respect- 

 ing the propagation of these algae under the microscope, 

 for the culture of Diatoms in cells is conducted in a manner 

 identical with that which the operator has practised in the labora- 

 tory, whether in a glass vessel or in other receptacles. But I ought 

 to add that if the manipulations required by the cultures under the 

 microscope are a little more difficult, they require special arrange- 

 ments and cells of a peculiar form, permitting — 



First — The keeping easily during many months the fecundated 

 macerations. 



Second — The observation of the living Diatoms with objectives 

 of the lowest powers as well as with the most powerful immersion 

 objectives. 



Third — The photographing the general appearance of the 

 growths, and the phenomena of the life of the Diatom. 



Optical arrangement. — This arrangement has been made, 

 according to my instruction, by Alf. Nachet. It is composed of a 

 horizontal, photo-micrographical arrangement of short length, 

 provided for the observation and study of the cultures, with a 

 tube carrying the objective perpendicular to the optical axis, in 

 which a prism of total reflection directs the luminous rays at will. 

 This microscope, adapted both for study and photo-micrography, 

 admits of all kinds of illuminations, and especially of a large 

 achromatic condenser with a focus of from three to four centi- 

 metres, capable of transmitting very intense luminous rays through 

 the cells ; in a word, strongly lighting up the objects that are to be 

 reproduced by photography. The cells containing the culture are 

 held on a plate, movable and vertical, while the interior is exam- 

 ined through a cover-glass of about 0*15 mm. of thickness. 



I have so fully described the microscope in the Annual of the 



