452 TRANSACTIONS OF THE CANADIAN INSTITUTE. [Versi 
acid, which dissolves everything else in the cell. Through the chroma- 
tophore stretch radial strands of protoplasm from the central body to 
the plasma zone on the inner wall of the cell. In pepsin and hydro- 
chloric acid the volume of the contents is greatly decreased, but this is 
not due to digestion of the peripheral portions chiefly and of the central 
body partly as Zacharias and others believed, but to a contraction which 
he terms enzymatic and which can be demonstrated in Sfzrogyra also. 
In the shrunken parts the peripheral as well as the central parts are 
present. Digestion experiments, therefore, give no certain conclusions 
as to the special nature of the central body. The latter is in his view 
simply a portion of the protoplasm enclosed by the chromatophore and 
containing assimilation products. There is nothing to indicate that it is 
a nucleus or the homologue of a nucleus. Nor is there any other organ 
which may be held to represent a nucleus. 
II—METHODS OF STUDY AND MATERIAL EMPLOYED. 
By hardening and staining highly organized animal and vegetable 
cells in the way that cytologists usually employ, one may obtain pre- 
parations which readily reveal the structure of these elements, but the 
employment of these and other simple methods in the case of the Cya- 
nophycez are not at all as fruitful in results. One finds in such little 
more than one can recognize in the living cells. It is with such and 
similarly meagre methods that the majority of investigators in this field 
of research have contented themselves when the apparently indifferen- 
tiated character of the cells in these organisms should have suggested 
the employment of a multiplicity of methods. It is only in this way 
that one may obtain results which permit a generalization concerning 
the structure of these forms. 
The Cyanophycez respond very sensitively to the conditions to which 
they are subjected. This fact also has been overlooked or not suspected, 
In a culture of them twenty-four hours will make a complete change in 
some of the more important features of their cells, and at the same time 
different parts of the same culture, not more than a few centimetres dis- 
tant from each other, may present specimens of the same species in 
which the cell contents are markedly unlike. It is to this fact that we may 
attribute discrepancies in.the descriptions, by the various observers, of 
the structure of these organisms. To illustrate particularly how impor- 
tant this point is, | may refer to Palla’s observations on Gleotricha 
pisum. In single cells of this form he found large vacuoles, and more 
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