Vol. 2] Gardner. — Cytological Studies in Cyanophyceae. 259 



are expressed, and the appearance of the illustrations represent- 

 ing the material from which the conclusions were drawn, it seems 

 that the existence of a karyokinetic process as here set forth is 



exceedingly doubtful. . 



From my experience in working on the same organisms it is 

 manifest that the chief trouble which has confronted these in- 

 vestigators and obscured the truth, thus preventing a unanimous 

 verdict, is the failure to discover a method which would clearly, 

 definitely, and unmistakably differentiate the structures which 

 are present. Because of this state of affairs, they have attempted 

 to harness to a comparatively simple process of nuclear division 

 the complicated mitotic process of the higher organisms, with its 

 formation of spireme, chromosome, spindle, etc. 



III. THE CELL CONTENTS. 



The study of the protoplast of the Cyanophyceae cell has re- 

 vealed to the writer the presence of the following structures, some 

 of which are constant, while others may or may not be present, 

 according to conditions which have not yet been definitely deter- 

 mined. First, there is a structure in the center of the cell which 

 occupies a larger or smaller portion of the cell, according to the 

 species; and its form is largely determined by the form of the 

 cell. The degree of its demarcation from the surrounding ele- 

 ments is a variable factor. In Oscillatoria margaritifera, for 

 example, the line of separation is not sharply defined, while in 

 Cylindrospermum the line is as sharply defined as in some of the 

 higher plants. On account of its appearance in the living cell, its 

 reaction to stains and its chemical composition, I have decided to 

 call this the cell-nucleus. Second, surrounding the nucleus and 

 extending to the cell-wall is the cytoplasm, which varies in struc- 

 ture slightly in different species, as well as in the same species, 

 according to the amount of the third kind of structure present, 

 viz., the granules. Incidentally, other structures have been noted 

 in certain species, for example, more or less cylindrical refractive 

 bodies in the cytoplasm of Oscillatoria ckalybea, to which I have 

 given no name nor ascribed any function. These do not occur 

 in every collection of the species, but when present in a collection 



