[348] 



tTecbnoIoo^ of Biatome/ 



By Mons. J. Tempere. 



Conclusion. 



The Selection— The Mounting of Isolated Specimens 



and Systematic Preparation. 



A COLLECTION of Diatoms to be really useful, so that it 

 may serve as a means for comparing species — their affin- 

 ities, transformation, etc., etc. — ought to be as much as 

 possible of isolated, well-marked individuals, so as to be capable 

 of being classed in a systematic manner. 



At first it seems very difficult to be able to take hold of and 

 transfer microscopic bodies so small as the greater part of the 

 Diatoms, and yet it can be attained with less effort than might 

 have been supposed. Certain arrangements, and a little practice 

 and patience, will suffice, as we shall presently see. 



The deposit and gathering, washed and held in suspension in 

 very pure distilled water, are spread either on microscopic slips or 

 on cover-glasses that serve to support them. If cover-glasses are 

 used, I give the preference to those of from 15 to 18 mm. diam- 

 eter, No. 2, that is to say, rather thick, which when once covered 

 with Diatoms can be preserved, if they are deemed, suitable, in 

 little boxes of 17 or 18 mm. diameter, and separated one from 

 the other by rings of caoutchouc or of card, which can be easily 

 obtained. 



If the spreading be made on micro-slips, which I prefer, they 

 ought not to exceed from 18 to 20 mm. to the centre ; then these 

 slips may be placed one on the other, separated by small pieces of 

 gummed card fixed at the end of each slip. 



To conduct the selection under the most favourable condition, 

 and without risk of confounding the species, it is necessary to use 

 an optical combination, giving at the same time an enlargement of 

 from 80 to 100 mm. in diameter, and a focus long enough to allow 

 the operator free manipulation of the instruments by which he takes 

 hold and transfers the Diatoms. The longer the focus of the lens, 



* Translated from Le Diatoniiste. 



