ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 619 



action of the fixing agent. The absolute alcohol material was after 

 2 days transferred to methylated spirit for a week, and then preserved in 

 a mixture of equal parts of absolute alcohol, glycerin, and distilled water. 

 The material fixed in Flemming's fluid was placed after about 2 hours 

 in 5 p.c. chromic acid for 16-18 hours, and then washed in running 

 water for several hours. The material was finally passed through up- 

 graded alcohols into methylated spirit, left there for a week, and after- 

 wards transferred to the same preserving fluid as before. To prepare 

 for sectioning, as much extraneous tissue as possible was removed from 

 the ovules, which were then passed through absolute alcohol, bergamot- 

 oil, to paraffin of various melting-points, being cut finally in 52° m.p. 

 paraffin. 



The sections, mostly 16 /x thick, were stained with Flemming's triple 

 stain and Ehrlich's haematoxylin. The former was more effective for 

 nuclear fusion, the latter for the pollen-tubes. 



Demonstrating Life-history of Leucocytes.* — C. E. Walker fixed 

 the material with Flemming's fluid (strong formula), Hermann's fluid, 

 acetic acid and absolute alcohol, corrosive sublimate and acetic acid, and 

 strong formic acid. The author remarks that the greatest care must be 

 taken with the processes of fixation, dehydration, imbedding, stain- 

 ing, etc. Extremely small pieces of tissue should be placed in the 

 fixative within about a minute of the death of the animal or removal 

 from the living body. Dehydration should be carried out in short 

 stages, an increase of 10 p.c. of alcohol being perhaps best. This does 

 not apply to tissues fixed in acetic acid and alcohol or strong formic acid 

 (10 p.c), from which the tissues are transferred immediately to absolute 

 alcohol. At the same time, it is necessary that the tissues should not be 

 left in alcohol (under 80 p.c.) for more than two or three hours after 

 fixation. In imbedding, no higher temperature than 45° C. should be 

 used. Throughout the processes of staining and mounting, the greatest 

 care must be taken that the sections do not become even partially dried 

 upon the slides. 



It is almost necessary to use a 10-inch tube Microscope with 

 monochromatic light and apochromatic objective and eye-piece. With 

 a monochromatic light it is possible to obtain excellent definition with 

 a 27- or even 40-compensation ocular, and a 2 or 3 mm. apochromatic 

 objective. Anything approaching this is impossible with the ordinary 

 short tube. 



In view of the advantage gained by using a monochromatic light, 

 the stains must be chcsen with regard to the colour of the light 

 used. The part of the spectrum between the blue and green gives 

 the shortest wave-lengths that can be conveniently used. As this gives 

 a better definition than the parts of the spectrum with longer wave- 

 lengths, red, yellow, and orange stains give the best results. 



Studying the Spinal and Sympathetic Ganglion Cells of the 

 Frog.f — E. Warfuringe fixed some of the material with 96 p.c. alcohol 

 and 2 p.c. ammonia, the rest with 40 p.c. alcohol and 2 p.c. ammonia. 



* Proc. Roy. Soc, Series B, lxxviii. (1906) pp. 53-9 (4 pis.), 

 t Archiv Mikrosk. Anat., lxviii. (1906) pp. 432-40 (1 pi.). 



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