420 F. R. ROWLEY ON SOME POINTS IN THE STRUCTURE 



prolongations of the central mass towards the periphery of the 

 cell exhibited a very beautiful longitudinal striation, while the 

 protoplasmic processes occupying the transverse canals mentioned 

 in my previous paper appeared to consist of five or six long rows 

 of cellular compartments. 



Another interesting feature is the presence of short paired 

 rod-like bodies in the central protoplasm of such Pinnidariae 

 as P. viridis, major, and nohilis (Fig. 2, dst). These rods (" Doppel- 

 stabchen ") are connected with a plexus of anastomosing fibrils 

 situated between the chromatophore and the cell membrane 

 (Fig. 2,/). At the commencement of mitosis these rods and 

 fibrils exhibit a radial arrangement with respect to the nucleus. 



An irregular anastomosing system of fibrils occurring between 

 the cell wall and chromatophore has also been observed in 

 Surirella (Fig. 4,/), but bodies corresponding to the paired rods 

 in Pinnularia have not been observed when the nucleus is in the 

 resting condition, though they appear in considerable numbers 

 when the central mass of protoplasm moves towards the broad 

 end of the cell in the initial stage of division. In many cases, 

 these little rods are placed parallel to the fibrillae which radiate 

 from the centrosome and poles of the spindle into the surrounding- 

 protoplasm. 



If the fibrillar plexus in either of the forms described above be 

 observed carefully, it will be noticed that individual fibrils possess 

 the power of independent movement, sometimes twisting in a 

 lively fashion or moving in an oscillatory manner. Under 

 unfavourable conditions, as when confined for some time under 

 a cover -glass with consequent lack of oxygen, they swell up and 

 lose their identity in a vast number of small refractive globules- 

 It is difiicult to fix these elements of the cell satisfactorily ; 

 the most perfect preservation of form and arrangement being 

 obtained by using chromo-aoeto-osmic acid, or sublimate, as a 

 fixative. 



Lauterborn points out that these protoplasmic fibrils are not 

 confined to the Diatomaceae, but appear to have an extensive 

 distribution in plant cells. Similar structures have been observed 

 by Berthold in Bryopsis, and by Frank Schwarz in a large-celled 



