126 
ON THE SPERMATOGENESIS OF THE SILK-WORM. 
formic acid, Rabl’s platinum chloride, chromo-platinum chlo¬ 
ride, i% formic acid, and Flemming’s chromo-osmium acetic acid. 
Of all these Flemming’s strong solution gives excellent 
results on fixing the nuclear elements and the cytoplasm. 
For staining the nuclear elements Flemming’s anilin-water 
safranin solution, and Hermann’s triple staining is mostly 
employed, while the cytoplasm is best stained by Böhmer’s 
hæmatoxylin. Most of my figures are, therefore, drawn from 
preparations fixed by Flemming’s solution and stained by 
these reagents. For killing embryos i% formic acid solution 
gives the best result. It not only preserves genital elements ex¬ 
cellently, but other tissues are also very well preserved. Picro- 
acetic acid is not very bad, but it causes the swelling of the 
chromosomes, sometimes so intensely that it is impossible to 
calculate their number; especially the longitudinal splitting of 
chromosomes is utterly destroyed by its use. 
For mounting sections, I used Gulland’s method, as it is 
modified by Mr. S. Ikeda formerly assistant in the laboratory. 
This is as follows :— 
A very thin and even layer of the fixative (Mayer’s albumen) 
is painted on the slide and a little distilled water is poured 
upon it. The sections are then placed on the slide, the 
excess of the water is wiped off with blotting paper and the 
slide is warmed in an oven of about 30-55°C. until the water 
completely evaporates. After this, it is treated as usual, 
mounted and stained. By this method there is no need of a 
section-smoother, as the rolling of sections may be completely 
prevented and the position of sections may be changed at will 
while we are placing them on a slide. In Gulland’s method, 
the same effect may be obtained, but the fixing of sections on 
a slide is not so strong, so that sometimes sections are remov¬ 
ed when treated with alcohol, but in this method such a risk 
is avoided. 
Before going into the description of the spermatogenesis, 
let us briefly describe the structure of the genital organs of 
the silk-worm in the larval stage, although the same subject 
has been treated of by other authors such as Cornalia (5), 
Verson (38, 39), and Haberlandt (11). 
The testes are paired, kidney-shaped, and lie at the right 
