248 ON THE STRUCTURE OF OSCILLATORI^. 



cells, I think, from the presence of the proper cell-membrane, 

 it might be reasonably inferred that the septa likewise con- 

 sisted of cellulose, though diflficult of positive demonstration 

 on account of their minute and delicate structure. On the 

 other hand, I must not omit to mention that I witnessed what 

 would lead one to think tliat a kind of immediate contact 

 existed between the cell contents ; so soon as the points a and 

 b in fig. 8, which represents a part of a filament under the 

 action of iodine, began to recede from the cross-markings, the 

 opposite portions in the intermediate adjoining cells retracted 

 simultaneously, just as if a separation had taken place. 



The axis of the filament may be compared to the pith or 

 medullary sheath (stratum medullare) of the Dicotyledons ; it 

 is solid, highly refractive, but slightly affected by iodine, and, 

 under a very high power, a granular appearance may be 

 distinctly seen in the very centre when the filaments are 

 broken up, and a single joint, which on end resembles a 

 lenticular disc, is examined. If the filaments are allowed to 

 dry spontaneously on a glass slide, a greenish thread may, 

 with a little care, be traced running through the middle of the 

 filament from one end to another. This is more decidedly 

 the case if the filaments have been previously treated by 

 iodine, fig. 10. While moist, no trace of this thread is to be 

 seen, owing to its being almost colourless, and rendered trans- 

 parent by the water ; after desiccation, however, it acquires 

 colour by condensation or shrinking, and becomes visible ; 

 sometimes, also, it will be found protruding, and in other 

 instances I have seen it keeping up the connexion of cells, 

 otherwise separated, fig. 11. After the addition of a weak 

 syrup, I have also frequently observed an appearance which 

 seems to countenance the view I have taken, and is shown in 

 fig- 4- 



With regard to their propagation nothing positive is known. 

 If kept for some time they gradually lose their green colour ; 

 those exposed to the sun much sooner, I think, than others 

 less exposed to its direct rays ; the stratum eventually be- 

 coming brown, sinks to the bottom of the containing vessel ; 

 it presents a granular layer, embodying great numbers of 

 filaments in all stages of decay, and, what is very singular, a 

 great number of Amah(P will be found feasting on them, with 

 swarms of lively Infusoria of the Monadina kind, briskly 

 flourishing their single flagelliform cilium about in all direc- 

 tions. I must also mention here a modification the filaments 

 are sometimes observed to undergo, which is represented in 

 figs 12 and 13. Some of the cells, namely, contract in the 

 middle, and their colour becomes much deeper and more 



