2G8 



THE MICROSCOPE. 



in the filament, and which divide it into distinct joints 

 or cells. 



The presence of this cell-membrane may be best de- 

 monstrated by breaking up the filaments, either by moving 

 the thin glass cover, or by cutting through a mass of them 

 in all directions with a fine dissecting knife. On now 



examining the slide, in most in- 

 stances many detached empty 

 pieces of this cell-membrane, with 

 its striae, will be found, as well 

 as filaments partly deprived of 

 the protoplasm, showing in those 

 places the empty, striated cel- 

 lnlin coat. On the application 

 of iodine all these appearances 

 become unmistakably evident ; 

 the greater portions of the fila- 

 ment turning brown or red, while 

 the empty cells, with their striae, 

 remain either unaffected, or at 

 most present a slight yellowish 

 tint, as is frequently the case 

 with cellulose when old. 

 With regard to the contents of the cell, the protoplasm 

 (or endochrome) is coloured in the Oscillatorice, and is de- 

 posited within it in the form of circular bands or rings 

 around the axis of the cylindrical filament ; iodine turns 

 them brown or red, and syrup and ddute sulphuric acid 

 produce a beautiful rose colour. As to their mode of pro- 

 pagation, nothing positive is known. If kept for some 

 time they gradually lose their green colour — those exposed 

 to the sun, much sooner than others less exposed ; the 

 stratum eventually becoming brown, sinks to the bottom 

 of the vessel, and presents a granular layer, embodying 

 great numbers of filaments in all stages of decay.* 



The movements oi the Oscillatorioe are indeed very sin- 

 gular, so much so that it is in vain to attempt to explain 

 them as altogether dependent on physical causes, and 

 equally so to show that they are due to a sarcode or animal 



* Dr. F. d'Alquen, "On the Structure of the Oscillatoriae," Journal of 

 Microscopical Science, voL iv. p. 245. 1S56. 



Fig. 146. — Mesoglia rermiciilaris, 

 composed of strings of cells co- 

 hering end to end. 



