ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 575 



be as small in quantity as possible in order to prevent the animals 

 swimming away during the process, which is entirely carried on under 

 the cover-glass. After the cover-glass has been put on a drop of a 

 1 per cent, solution of osmic acid is added and sucked through from 

 the other side, then water, 70 per cent, and 90 per cent, alcohol, 

 and finally water again. For the colouring of the now sufficiently 

 hardened and fixed animals, Weigert's picrocarmine process * is 

 recommended. This should act an hour and a half to two hours, the 

 preparation being placed in a moist chamber in order to prevent 

 drying. After removal of the colour 70 per cent., 90 per cent., and 

 absolute alcohol, oil of cloves, and finally Canada balsam are added. 



This process, which in reality takes only a short time, gives very 

 excellent results for many Infusoria. In the case of others, however, 

 the use of osmic acid is not so good, and with Amoebce it is entirely 

 without result. For these organisms, therefore, a 2 per cent, solution 

 of chromic acid is preferable, which must act for two to three minutes 

 in order to harden them sufficiently, otherwise in washing they 

 readily swell up and burst. The remaining process is the same as 

 the previous one. 



The duration of the action of the agents varies of course for 

 different animals, depending upon their size and fineness — the most 

 different Infusoria and Flagellata have been preserved in this way 

 without manifesting the slightest shrinking. The cilia and vacuoles 

 are quite life-like, and show the nucleus and nucleoli with an intense 

 red colour. By far the best result, however, of the method is, the 

 author considers, in its use for Amoebce, the preserving of which had 

 hitherto not succeeded. They are fixed in the position in which they 

 are at the moment of the chromic acid being added. Even in the 

 fine pseudopodia the vacuoles are easily to be recognized. The 

 nuclei are also distinctly coloured. 



In a postscript the author adds that Dr. A. Gruber, of the Frei- 

 burg Zoological Institute, who had previously found the process 

 very useful for Ehizopoda and allied organisms, has since tried it on 

 Heliozoa and found it to succeed excellently. 



Preserving Protozoal — Eeferring to the preceding paper, B. 

 Landsberg considers that it is a disadvantage that all the operations 

 have to be performed under the cover-glass. It is scarcely possible, 

 therefore, to prepare clean slides, as foreign bodies once under the 

 cover-glass cannot be removed. It is also to be doubted whether the 

 osmic acid can act with the necessary suddenness and in sufficient 

 concentration, and finally there is the danger of the object swimming 

 away. 



He therefore proposes a method which obviates all these incon- 

 veniences, and which even a beginner can soon learn. 



A small quantity of water being placed in a watch-glass or on a 

 slide (without a cover-glass), is observed under the Microscope, and 

 when an object is seen which it is desired to mount it is sucked 

 up by a fine pointed capillary tube, taking care to have a little 



* Arch. f. path. Anat. u. Physiol. (Virchow) Ixxxiv. 

 t Zool. Auzeig., v. (1882) pp. 336-7. 



