ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 833 



Bismarck-brown and auilin-violet. The sulution8 must bo perfectly 

 neutral. The Bisniarek-brovvn stains the organisms without affecting them, 

 while the auilin-violet stains and slowly kills them at the same time. In 

 diphcnylamine-blue in concentrated solution the animals swim about 

 uustaincd and uninjured, hence they show up well against a dark-blue 

 ground. 



For fixation, the aiithor advises osmic acid or a mixture of equal j^arts 

 of 1 per cent, osmic acid and 20 per cent, acetic acid. The animal to 

 be fixed should be ])laccd between slide and cover-glass and observed 

 through the Microscoije. When rendered sufficiently motionless by 

 pressure on the cover-glass this latter should be prevented from moving 

 by drops of molten paraffin. The fixative may then be run under the 

 cover-glass in the usual Avay. 



For staining the author recommends picrocarmine, Scale's carmine, 

 alum-carmine or methyl-green. If stained with methyl-green the sj^eci- 

 mens may be mounteil in dilute glycerin or Bram's fluid (water 100, 

 glycerin 10, glucose 40, camijliorated spirit 10). The index of refraction 

 of the latter is higher than that of the glycerin^ and is proportionately 

 more useful. 



The specimens may be mounted in balsam ; if so, care must be taken 

 to increase the strength of the dehydrating spirits very gradually ; then 

 creosote, and finally xylol-balsam. 



Investigation of Infusoria.* — Dr. W. Schewiakoff gives an account 

 of his method of studying Infusoria. He always began his observations 

 with living specimens, which were isolated in a drop of water and fixecv 

 to one spot. The necessary pressure was regulated by the removal or 

 addition of water. The best water in which to place the organisms is 

 that in which they were found, and which had been filtered. Observa- 

 tions can best be made on starving specimens. As soon as the animals 

 were comidetely free of food, artificial feeding was commenced ; this of 

 course varies with the habit of the infusorian ; those that live on uni- 

 cellular plants may well be provided with drops of animal fat, which 

 can be easily enough obtained by squeezing a small crustacean. Those 

 that live on Bacteria were provided with indigo or carmine which showed 

 up the characters of the digestive system. When the animals had had 

 enough food they were again placed in clean water and observed furtlier ; 

 by this means the position of the anus may, among other things, be made 

 out. 



By pressing on the cover-glass with a dissecting-needle the animal 

 is forced to break itself uj). As this happens the trichocysts may be 

 observed, the mouth and pharynx be more conveniently examined, and 

 the macro- and micro-nuclei isolated. 



To kill specimens the best reagent is the vapour of 1 per cent, osmic 

 acid ; larger forms, such as D'dcptus, must be put in finetubes with as 

 little water as possible and be jjlaced for some seconds in 1 per cent, 

 osmic acid, when death will be found to follow very suddenly. Pre- 

 i:)arations thus made are well adapted for the study of the striae of the 

 body and the protoplasmic structures. When cilia, setaj, or mem- 

 branellfe are to be studitd a 5-10 per cent, solution of soda is recom- 

 mended. The organisms should be put in glycerin when we desire to 

 study them from difi'erent sides. A solution of 1 per cent, acetic acid, 



* Bibliotheca Zool., v. (1880) pp. 5-7. 

 1889 3 M . 



