220 A. B. MACALLUM. 
cells generally, but the greater part appears to remain in the 
cytoplasm of the developing fibre, and undergoes a transforma- 
tion which is one of great interest in connection with the 
origin of hemoglobin. In the cytoplasm of the muscle-cells 
there is an abundance of yolk-spherules which, as in other 
cells, gradually undergo solution, the dissolved substance 
diffusing through the cytoplasm. When the striation makes 
its appearance at one side of the now elongated cell, the dis- 
solved substance passes into the striated area, for ammonium 
hydrogen sulphide brings out an iron reaction in this part as 
readily as in the undifferentiated cytoplasm and in the spherules, 
but confined to the dim bands, the light bands giving no 
evidence of the presence of the compound. In the fibre from 
which the spherules have all but disappeared, and in which the 
striated area embraces nearly the whole of its width, the reac- 
tion with ammonium hydrogen sulphide is as distinct and as 
marked as in the earlier stage, and this is true also of the fibre 
in its final form. In this stage the iron is quickly liberated by 
acid alcohols, as well as by ammonium hydrogen sulphide, and 
its presence may be readily demonstrated by means of these 
reagents up to the period when all traces of yolk disappear 
from the cells of the larve. After this date the iron compound 
becomes firmer, or, to speak more accurately, is less readily 
attacked by acid alcohols or the sulphide reagent, and in the 
muscle-fibre finally its presence may not be shown by these 
methods. It is not that the iron is removed from the fibre, 
but that the compound containing it is transformed, in red 
muscles, into what is called myo-hematin by MacMunn, or 
hemoglobin by Hoppe-Seyler and others. The latter com- 
pound can, by means of the staining fluid of Shakespeare and 
Norris, be clearly shown to be strictly confined to the dim 
bands, which are given a grass-green colour distinctive of 
hemoglobin, while the light bands and nuclei are coloured 
red.! 
1 T have pointed out the value of the reagent in this respect in my paper 
entitled ‘‘ Studies on the Blood of Amphibia,” ‘Transactions of the Canadian 
Institute,’ vol. i, 1898. 
