INVERTEBRATA, CRYPTOGAMIA, MICROSCOPY, ETC. 763 



in the atmospheric dust without being found in a living state in 

 adjoining water ; and thus Ehrenberg's question is answered. 



It is very possible that these diatoms belong to those in which the 

 phenomena of deduplication, conjugation, and formation of spores are 

 the most active, rapid, and easy to follow, and it is on this account 

 that the study of terrestrial diatoms deserves attention. 



The Eev. George Davidson, of Scotland, told M. Deby that for 

 several years he has searched mosses for diatoms, and has found 

 that the mosses growing at the foot of elms on the side exposed to the 

 north furnish the greatest number. 



MICEOSCOPY, &c. 



Method of preserving- Infusoria, &c.*— M. Cortes repeats in the 

 ' Journal de Micrographie ' the account of his observations, which 

 have already appeared in the ' Comptcs Eendus,' f to which he adds 

 the following remarks : — 



To obtain good preparations the following conditions must be 

 fulfilled. 



1. The absence of any movement of the cover-glass which could 

 crush the Infusoria. 



2. Bapid action of the osmic acid and complete elimination of the 

 reagent as soon as the desired action is obtained. 



3. Sloiv and progressive action of the colouring reagent, whatever 

 it is, and elimination of it by glycerine. 



4. Very slow substitution of the pure glycerine for the diluted and 

 coloured glycerine. 



5. Hermctical sealing, which cannot be obtained either with 

 paraffin or with sealing was dissolved in alcohol, or with Canada 

 balsam if the margins of the preparation are not perfectly dry. 



Haematoxylic Eosin and its emplojnnent in Histology. J — It is 



known that eosin, soluble in water, colours the i)rotoplasm of the cell 

 elements, without having any selective action for the nuclei, so that when 

 we wish to bring out these latter in a preparation coloured with eosin, 

 recourse must be had to the method of double colouring proposed in 

 1876 by Wissotsky, a method which is long and requires several 

 successive washings, which easily leads to the deterioration of the 

 sections. Moreover, alcoholic or aqueous solutions of eosin precipitate 

 that of hematoxylin prepared after Boehmer's classic formula. 



M. J. Eenaut, having remarked that eosin in an aqueous or 

 alcoholic solution does not precijntate the hematoxylin of Boehmer's 

 liquid, when the mixing is effected in the presence of neutral glyce- 

 rine, conceived the idea of employing a liquid prepared in this manner. 

 He mixes one part, by volume, of neutral glycerine and one part of a 

 saturated solution of eosin in alcohol or water (according as pure 

 eosin or eosin a la i^otasse is iised). There is then added drop by 

 drop hfematosylin prej)ared according to Boehmer's formula until the 



* ' Joimi. de Micr.,' iii. (1879) p. 242. 



t See this Journal, ii. (1879) p. 331. 



X 'Coraptes Keudus,' Ixsxviii. (1879) p. 1039. 



