ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 121 



pyroligneous acid, which, allowed to run in under the cover-glass 

 in small quantities, killed and fixed the organisms in their natural 

 form. 



After referring to the methods suggested by Certes,* Biitschli,f 

 and Thanh offer and Davida,J the author describes that which he 

 has adopted in the hope of obtaining the same beautiful results as 

 Duncker, but at the same time more durable. 



" According to my experience, various means, long known, are 

 adapted for fixing the smallest and most delicate organisms; for 

 instance, rectified pyroligneous acid, the 'liqueur salin hydrargy- 

 rique ' of Blanchard, in the mixture which Arnold Lang recommends 

 for preserving marine Planarians, § and which has been also used by 

 Paradi for fixing fresh- water Turbellarians with the best results; 

 also picric acid ; and lastly, what Paul Mayer has so strongly recom- 

 mended II for the lower animals, viz. picro-sulphuric acid, which 

 certainly should have the preference over the others. All these 

 media (the list of which is by no means exhausted), kill microscopical 

 organisms instantaneously, without destroying their organization. 

 Flagella and cilia, the suctorial disks of the Aeinetce., and even the 

 fine pseudopodia of the Heliozoa can be fixed as well as the pedicel of 

 the rapidly-jerking Vorticellce. Also the muscle of the pedicel, the 

 contractile vacuoles, and the oesophagus and digestive vacuoles. 

 Euglence and Amoebce may be fixed in their various changing shapes. 

 Eotifera die mostly with their peristomes moderately withdrawn, and 

 Vorticellce the same ; but examples may be obtained from Carchesium- 

 and Epistylis-stems, which are fixed in the act of lively rotation. 

 Infusoria are fixed in the same life-like state, in the act of fission or 

 conjugation, and Vorticellce in the bud form of conjugation. The 

 nucleated elements also come out very prominently, even the nucleolar 

 capsules can be splendidly preserved for further study, and their 

 striation retained. Spongillce, Hydrce, small Nematodes, Tardigrades, 

 delicate insect larvae, and ciliated cells (e. g. of the gills of mussels) 

 can be excellently fixed and preserved. To obtain durable prepara- 

 tions, however, it is absolutely necessary to remove the fluid which 

 has completed its work in the process of fixing, as it might injure the 

 fine organisms by longer action, afterwards placing the preparation in 

 a fluid which is suited to it. 



" My procedure is essentially the same as that which Paul Mayer 

 used for treating the lower marine animals with picro-sulphuric 

 acid. 



" I place the Protozoa and other microscopical organisms with 

 the Algse, sediment, or other objects to which they are affixed or 

 between which they move, with some water in a watch-glass, then 

 drop in a few drops of the fixing fluid, which I allow to act only 1-2 

 minutes. I then pour off the fluid carefully, or simply lift the 



* Oomptes Eendus, Ixsxviii. (1879) p. 433. See this Journal, ii. (1879") 

 pp. '331 and 763. 



t Zool. Jahresber., 1879, p. 173. 



X Thanhoffer, L. v., ' Das Mikroskop und seine Anwendimg,' 1880, p. 110. 



§ Zool. Anzeig., i. (1878) p. 14. See this Journal, i. (1878) p. 256. 



II MT. Zool. Stat. Neap., ii. (1880) pp. 1-27. 



