232 A. B. MACALLUM. 
is situated immediately under the membrane. Korschelt’s 
views on the structure of the filament are directly opposed 
to those of Leydig and Balbiani. He regards the transverse 
striation of the filament as due to a folding of the surface 
membrane only, and explains the longitudinal striation ob- 
served by Leydig as caused by the action of the reagents used. 
In his opinion, also, the apparent differentiation of the fila- 
ment is due to the differences in the reflected light. 
So far as I know, no one has hitherto observed an arrange- 
ment in the nuclear filament of Chironomus similar to that 
described by Leydig, although Carnoy has found in the salivary 
gland of a Nemocere larva that the dim disc is formed of a 
series of longitudinally disposed rodlets, but he attributed the 
delicate lines observed in the clear discs to folds in the mem- 
brane of the filament.? The larve of the species of Chirono- 
mus accessible to me offer preparations less favourable for 
study than do those of the species C. plumosus studied by 
Balbiani and Leydig, yet I have been able to determine, with 
my methods for demonstrating the presence of assimilated iron, 
the correctness of Leydig’s observations so faras they go. The 
dim discs are of different thicknesses, the thickest appearing 
to be five or six times the diameter of the narrowest. When 
the salivary gland, after being hardened in alcohol, is kept 
for several days in sulphuric acid alcohol, treatment with an 
acid ferrocyanide solution gives all these dim bands a deep 
blue reaction, the intensity of the reaction coming out very 
markedly in the thicker bands. Under the highest magnifica- 
tion of service in such a case (apochromatic immersion 
15 mm. and compensation ocular 8, Zeiss), the bands of 
medium thickness are resolved into a series of short rodlets 
disposed parallel with the filament. If the filament has, in 
the course of preparation, been isolated from the nucleus, one 
may then determine that the rodlets forming one dim band 
are connected by excessively delicate fibrils with the rodlets 
1 Ueber die eigenthiimlichen Bildung in den Zellkernen der Speicheldriisen 
von Chironomus plumosus,” ‘Zool. Anz.,’ vol. vii, pp. 189, 221, 241, 
1884, 
2 ¢ Biologie Cellulaire,’ p. 232. 
