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 Bohmer's 

 hasmatoxylin. 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 Comalia (5), 

 Verson (38, 39), and Haberlandt (11). 



The testes are paired, kidney-shaped, and lie at the right 



