ON THE STRUCTURE OF OSCILLATORI^. 247 



filaments plainly enclosed in their sheaths, and have in- 

 variably been able to demonstrate the different tissues referred 

 to, viz., the plain unstriated cellulose sheath, and the striated 

 special or proper cell-membrane of the filament, deprived of 

 its protoplasm. Moreover, the sheaths never have any striae 

 corresponding to the joints of the filament, and I am rather 

 inclined to think that other observers, mistaking the cell- 

 membrane for the enclosing sheath, have been prevented from 

 earlier establishing the presence of the former, because I am 

 convinced, as it has been stated that the sheaths seldom show 

 any strige, that, where these striae ivere observed, the cell- 

 membrane has been mistaken for the sheath. 



With regard to the contents of this cell-membrane, it has 

 already been stated that the protoplasm (or endochrome, since 

 it is coloured in the Oscillatoi'ifB) is deposited within it, in 

 the form of circular bands or rings, around the axis of the 

 cylindrical filament ; they are evidently of a nitrogenous com- 

 position, coloured by chlorophyll ; iodine turns them brown 

 or red, and syrup and dilute sulphuric acid produce a beau- 

 tiful rose colour. The cells seem, however, not uniformly 

 filled with it, but its deposition is in some places less dense 

 than in others, as, for instance, in the centre. This circum- 

 stance, as well as that the cells are formed round the solid 

 axis of the filament, must be borne in mind on examining the 

 filaments while under the action of various chemical reagents. 

 By means of these latter, I think, it may be satisfactorily 

 proved that the filaments are really composed of separate 

 cells ; syrup causes them to contract by e.rosmose, and, if it 

 is replaced by water, they resume their original shape by 

 e/Klosmose (figs, 4, 5, 6). Another question, however, is, are 

 these cells in simple apposition without an intervening cellu- 

 lose wall, or what kind of connexion, if any, exists between 

 them ? This question is not easily answered, but I am almost 

 convinced that the striae of the cell-membrane represent 

 distinct joints, forming a cellulose wall, as represented in the 

 ideal section, fig. 7 b, because I have never observed the 

 endochrome recede beyond the striae on the addition of a 

 strong solution of chloride of calcium; and the lenticular 

 disks (fig. 9), or single joints, when on end, can bear any 

 pressure short of their entire destruction without displacement 

 of the endochrome, which would hardly be the case if it wei'e 

 not enclosed within a proper cell. Further, in detached 

 empty pieces of the cell -membrane, some of the striae are 

 often seen out of their natural position, dividing the cells 

 obliquel}', having been ruptured ; and lastly, as there can be 

 hardly any doubt that the filaments consist of a series of 



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