774 SUMMARY OF CURRENT RESEARCHES RELATING TO 



l.otli stains penetrate the cell, but that one undergoes changes according 

 as the cell is alive or dead, so that only one stain is represented. The 

 author <, r ives as an example the central nucleus that stains blue in an other- 

 wise only red-stained cell, and to the blue-stained bacteria contained in 

 i lie nutrient vacuole of a red-stained amoeba, and concludes that both the 

 red and the blue stain are to be found in the stained object, and points 

 out that the simultaneous presence of both stains in the cell would be 

 demonstrated by the addition of hydrogen peroxide, a mixed violet 

 stain resulting. The author concludes that with the use of his mixed 

 stain, the methylen-blue is present in the living cell, and that the 

 neutral red is present in the dead cell, but by the chemical influence of 

 the protoplasm they are rendered invisible. And further, that the 

 neutral red staining of the living cell is a chemical process, whilst the 

 methylen-blue staining of a living cell is a vital phenomenon, but has a 

 physical basis. 



(5) Mounting, including- Slides, Preservative Fluids, &c. 



Method for Mounting Celloidin Sections.* — D. Cristina proposes the 

 following method. The sections, being cut and stained, are transferred 

 to alcohol at 94° for a short time ; from this reagent they are taken by 

 means of strips of blotting paper and transferred to specially prepared 

 glass slides : these have been spread with glycerinated albumen (egg 

 albumen 5 parts, neutral glycerin 1 part) ; the paper strip with the 

 sections attached is laid, section side down, on the prepared surface of 

 the slide, other dry strips being laid over it and gentle pressure made 

 with the finger. The sections remain firmly fixed. 



Method of Staining and Permanently Preserving Urinary 

 Sediment.f — P. Fiorentini and M. Signer stain the deposit obtained by 

 centrifuging or by sedimentation with the Ehrlich triacid mixture, and 

 then treat the material with glycerin slightly acidulated. Treated in 

 this way permanent and cntrast-stained preparations of urinary deposit 

 are easily obtained. The authors are vague as to time and acidity. 



(6) Miscellaneous. 



Keeping Polyzoa.}— F. St. John Parker hit upon the idea of taking 

 only a few small colonies and dividing these among several aquaria, thus 

 allowing the groups ample room. He found this plan answered perfectly, 

 and he writes : — " I can keep Polyzoa in captivity for very much longer 

 periods than I found possible before adopting my present plan. Last 

 September I found some specimens of Fredericella sultana, some of 

 which were alive in March this year, when an accident unfortunately 

 destroyed them. I have at present a number of small, but flourishing, 

 colonies of both Fredericella and Plumatella repens in the small square 

 glass tanks which can be bought at Beck's for about 8s. each. Small 

 groups of about half-a-dozen or so individuals are all that are needed 

 for the Microscope to make a really fine display, under dark-ground 



* Zeitschr. wise. Mikrosk., xxii. (1904) p. 99. 



+ Tom. cit., pp. 187-9 (1 pi.). 



X English Mechanic, lxxxii (1905) p. 187. 



