NOTES AND MEMORANDA. 331 



older Societies which covered the same ground, there has been 

 found to be room for another mainly devoting itself to the larger 

 animals — the Vertebrata, and in the same way there was obviously 

 room for one mainly devoting itself to the smaller animals — the 

 Invertebrata, and to the development and minuter structure of the 

 higher forms. 



We therefore should define " Microscopy " as the science and art 

 of the Microscope as an instrument both in regard to its theoretical 

 principles and its practical working ; but a " Microscopical " Society, 

 as a Society established on the one hand for the improvement of the 

 Microscope and the methods of its application (" Microscopy " proper), 

 and also for the communication of observations and discoveries in the 

 various branches of Biology (Invertebrata, Cryptogamia, Embryology, 

 Histology, &c.), which more especially require the aid of the Micro- 

 scope for their investigation. 



Oil-Immersion Objectives. — We are glad to find that the English 

 opticians are at length turning their attention to these objectives, 

 which ithas hitherto been impossible to procure of English manufacture, 

 although we believe we are correct in saying that their construction 

 was primarily urged upon opticians in this country when the idea first 

 suggested itself of the desirability of oil objectives. 



Messrs. Powell and Lealand exhibited at the meeting of the 

 Society on the 9 th April, an i oil-immersion objective of their manu- 

 facture, and we believe that the construction of higher powers is being 

 proceeded with. 



Method of Preserving Infusoria, &c. — A note by M. A. Certes in 

 ' Comptes Kendus ' * describes a method of obtaining permanent 

 preparations of the Infusoria, which he hopes may help to create col- 

 lections of which all the Museums of Europe are at present deficient. 



The method which he suggests is the employment of the vapour or 

 a solution of osmic acid (2 per cent.), the former, although well known 

 in histology, " never yet having been applied to the Infusoria," | and 

 he claims that the organisms are instantaneously fixed, so that the least 

 details, cilia, cirrhi, flagella, and buccal armatui-e may bo observed 

 with the highest powers, the Euglente and Paramecia preserving their 

 characteristic colour. The nucleus and nucleolus stand out clearly, 

 and show, when these occur, the curious phenomena described by 

 Balbiani. The process may be applied successfully not only to the In- 

 fusoria, but also to the Eotatoria, Anguillulfe, Bacteria, and Vibrions. 



The important point is to make the osmic acid act proiuj^tly 

 and with a certain force. Two means are available for obtaining 

 this result with some certainty. The first, which is suitable for 

 most cases, consists in exposing the Infusoria to the vapours of the 

 acid for a period of from ten to thirty minutes. For very contractile 

 Infusoria the process is different, the immediate contact of the osmic 

 acid being obtained by putting a drop of the solution on the cover- 

 glass before placing the latter on the di'op of water. The excess 



* ' Comptes Rendus,' ixxxviii. (1879) 433. 



t Compare, however, Dr. Pelletan's process — this Journal, i. (187S) 189. Also 

 Huxley and Martin's ' Biology.' 



