IRON COMPOUNDS IN ANIMAL AND VEGETABLE CELLS. 247 
Raum are, however, much more common elements than these, 
and are to all appearances quite different structures, as is 
apparent in ordinary cover-glass preparations made after 
Raum’s methods. The larger examples of the granules of 
Raum seem to be less abundant in corrosive sublimate prepa- 
rations stained with hematoxylin and eosin. 
From these results I am inclined to regard the existence of 
a nucleus in the yeast-cell, in its usual condition, as extremely 
doubtful, and, on the other hand, to support Krasser’s con- 
tention that nuclein is disseminated through the cytoplasm. 
Whether, in other stages, as, for example, those in which spore 
formation occurs, there is a nucleus I cannot say, but there 
appears in the ordinary stages of the organism to be nothing 
which may be looked upon as a specialised chromatin-holding 
structure. 
These conclusions are, on the whole, confirmed by the 
results of experiments made to determine the distribution 
of assimilated compounds of iron in these organisms. When 
specimens of S. cerevisiz, hardened in alcohol, are subjected 
to the action of the glycerine and sulphide mixture at a tem- 
perature of 60° C. for several days, their cytoplasm acquires a 
greenish tint. Sometimes, however, the latter reaction may 
not appear except in a few granules scattered through the 
cytoplasm (fig. 4). On account of the small size of the cells 
and of the alteration produced in them by the reagent, one 
cannot definitely determine whether the granules correspond 
to those described by Raum. When the cells have been sub- 
jected to the action of sulphuric acid alcohol, the subsequent 
application of an acid ferrocyanide solution gives their cyto- 
plasm a faint blue colour, which is more distinct and deeper 
when the light transmitted passes through several cells in 
succession. Blue granules are sometimes observed in such 
preparations. 
It is in specimens of S. Ludwigii that one obtains the 
clearest evidence of the occurrence of an assimilated iron 
compound. In these, after being hardened in alcohol, the 
glycerine and sulphide mixture eventually gives results like 
