CHAPTER XXV 



A HUNDRED MICROSCOPICAL OBJECTS OF 

 BIOLOGICAL INTEREST 



The following list of a hundred objects for the microscope 

 includes preparations considered to be of more or less 

 value to pure biology. Some have not been tested by the 

 writer, but are suggested on good grounds. Some are 

 temporary preparations, made only for purposes of study. 

 The employment of the preparations for further investiga- 

 tion is sometimes suggested. An indication of the litera- 

 ture is often given. 



PLANT OBJECTS 



1. Chromosomes with Chromomeres, in the Embryo Sac 



of Galtonia candicans. — Embryo sacs are to be cut open at 

 the right stage. This can be determined by putting pieces 

 of the walls into iron-acetocarmine, and examining for 

 division stages of the endosperm nuclei. The writer fixed 

 the opened ovules in Hermann's mixture, and stained with 

 Mayer's hsemalum; but it would probably be as well to 

 fix with chrom-acetic-formalin and stain w^ith iron-brazilin, 

 or iron-hsematoxylin in 70 per cent alcohol. The air pump 

 may be needed to remove bubbles from the opened embryo 

 sacs. After fixing, the endosperm layer is to be dissected 

 out in weak alcohol, stained, flattened, and mounted in 

 (balsam or) immersion oil, under a cover-glass 0.17 milli- 

 meter thick, on a slide of standard thickness. It is to be 

 viewed with yellow-green or blue-green light, and a fluorite 

 or apochromatic oil-immersion objective of 1.3 aperture, 

 with Jsj 01' ?fo condenser cone. More investigation is 

 needed on chromomeres, as to their numbers and appear- 

 ance in somatic chromosomes. (Strasburger, S. Nawaschin, 

 Newton, Belling.) 



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