238 A. B. MACALLUM. 
Stentor and Paramecium, in sufficiently large numbers, 
and all but completely free from inorganic iron compounds, 
were readily obtained. The cytoplasm in Vorticella, on the 
other hand, usually contains such compounds, but these 
are very often in the form of granules situated in vacuoles, or 
at the periphery of the same, a disposition of the compounds 
which gives every facility for studying the distribution of the 
assimilated iron. 
In the examples of Epistylis there were, as stated, no in- 
organic compounds of iron, at least none were demonstrable 
in the glycerine and sulphide mixture within the first hour 
after the application of the reagent, but on the third and fourth 
day both cytoplasm and nucleus gave a marked reaction for 
iron. The latter was, of course, most prominent in the nucleus, 
in which was revealed, by the dark-green colour, in some exam- 
ples a granular structure, in others a fibrillar arrangement. 
The reaction of the cytoplasm was a diffuse one, with here and 
there large granules in which it had developed more markedly. 
The membrane and stalk were, in these cases, free from iron. 
All these points were more readily observed in preparations 
treated with sulphuric acid alcohol or with Bunge’s fluid for 
twenty-four hours (fig. 28). 
In Vorticella a similar distribution of the assimilated iron 
was observed in both cytoplasm and nucleus, and a diffuse 
reaction for iron was also obtained in the central or axial por- 
tion of the stalk, after the preparation had been kept in the 
warm glycerine and sulphide mixture for several days. The 
reactions are represented in fig. 27, drawn from a preparation 
which contained inorganic iron compounds disposed in vacuoles. 
In this the central portion of the stalk is shown to be continued 
into a funnel-shaped organ at the base, which also contains 
“masked” iron. Iwas unable to determine how this organ 
was connected with the cytoplasm. I found no difficulty in 
obtaining the complete reaction in all the parts at the end of 
a five days’ application of the warm glycerine and sulphide 
reagent. 
Examples of Stentor polymorphus, free from inorganic 
