254 A. B. MACALLUM. 
all, of the iron-holding substance, and with this the character 
of the nuclei seems to change. The “nucleoli,” first of 
all, are converted into fine granules distributed through the 
nuclear cavity, and, finally, in the mature gonidia the nuclei 
appear, in the glycerine and sulphide preparations, to be 
simply more or less homogeneous masses of iron-holding sub- 
stance, while the cytoplasm does not contain a trace of the 
metal (fig. 6 /). 
In Aspergillus glaucus the cytoplasm of the young 
mycelia and the gonidiophores, especially their globular ends, 
absorbs staining matters readily, but it contains also, scat- 
tered through it, granules of a nucleolar character, which, 
in very dilute solutions of hematoxylin, applied for twenty- 
four hours or more, stain deeply. The cytoplasm of the 
sterigmata and of the immature gonidia is similarly affected. 
In the mature gonidia hematoxylin selects large granules 
which are distributed through the cytoplasm. In what appear 
to be old mycelial threads, the cytoplasm is stained with diffi- 
culty, while the membrane may be deeply coloured. These 
results correspond in the main with those obtained in regard 
to the ‘‘ masked” iron present. When the warm glycerine 
and sulphide mixture is applied for about a week, the cyto- 
plasm of young mycelia gives a diffuse reaction for iron, while 
a deeper one appears in the large granules referred to as 
affected by hematoxylin. In the cytoplasm and granules 
of the gonidiophores a relatively deeper reaction makes its 
appearance, and a marked one is obtained in the sterigmata. 
In the immature gonidia the reaction is diffuse, a special one 
at the same time obtaining in granules collected or scattered 
in the cytoplasm. In mature gonidia the granules are larger, 
and give a deeper reaction for iron, the cytoplasm otherwise 
showing no trace of its presence (fig. 7). The same results 
are obtained, but more readily, when sulphuric acid alcohol 
has been employed to liberate the iron present. 
Bacteria.—The question of the occurrence in bacteria 
of a substance like the chromatin of more highly developed 
organisms has been investigated to a certain extent by 
