1891.] Microscopy. 87 
the yolk dissolves, and the cortical layer with the germ can thus be 
easily isolated. After several days the preparation is to be carefully 
washed and passed through several grades of alcohol. 
This process does very well for the earlier stages, but not so well for 
the later ones, as the osmic acid does not penetrate the more advanced 
embryos sufficiently. : 
2. The method that proved the best was as follows: The egg is im- 
mersed for ten minutes in Kleinenberg’s fluid, to which has been added 
one-tenth its volume of glacial acetic acid ; it is then opened in ten 
per cent, acetic acid, which dissolves the yolk, and thus enables one to 
isolate the germ. The germ is next placed in Kleinenberg’s fluid for 
several hours, then in alcohol. 
Bryozoa.’—In studying the process of budding in Pedicellina, 
Loxosoma, and other Bryozoa, Dr. Oswald Seeliger made use of cor- 
rosive sublimate (saturated solution in hot sea-water), usually in com- 
bination with one-fiftieth its volume of glacial acetic acid. This mixture 
was used cold, and allowed to act from five to eight minutes. The 
preparation was thoroughly washed and stained with borax-carmine. 
To this sublimate-acetic acid mixture was sometimes added chromic 
acid (one-tenth per cent.), with the result that the epithelial structure 
was well preserved but difficult to stain. 
Caryokinesis in Paramecium.'—In the study of Paramecium 
Prof. R. Hertwig made use of picro-acetic acid, chromic acid, and 
chrom-osmic acid as hardening reagents. Picro-acetic acid followed by 
borax-carmine was the principal method. The staining process was 
aided by the heat of an incubator, and decoloration was effected by 
alcohol acidulated with “hydrochloric acid. The preparation was 
mounted in glycerine or in clove oil. Clove oil is preferable to 
Isam, as it reveals more clearly the fibrous structure of the spindle, 
and allows of turning and pressing the object at any time. 
Clove oil causes the cytoplasm to become brittle, so that the body 
of the infusorian may be broken up by pressure or blows on the cover- 
glass, and thus the nuclear spindles be set completely free. In this 
isolated condition they can be studied to the best advantage, as they 
are not obscured by overlying cytoplasm. 
For the study of the achromatic figures clove oil is too strong a 
clarifying medium. Glycerine or water will serve better. Hertwig 
figures, washed in alcohol, and mounted in glycerine. He was thus 
able to study all parts of the figures under most favorable conditions. 
Š Zeitschrift f. wiss. Zoologie, XLIX., 1, 1889, pp- 168-9; and L., 4, 1890, p. 561. 
ëR. Hertwig. Conjugation d. Infusorien. Abhl. d. k. bayer. Akad. d. Wiss., II. Cl., 
