fi'om the Cell-contents of the Characese. 113 



Happening one day to be examining the spores of CladophorUy 

 with which Conferva^ QLdogonium, and this Oscillatoria had been 

 mixed and kept in a glass for eight or ten months, for the sake 

 of observing the development of the former, I noticed that in 

 several of the filaments of the Oscillatoria there were green cells 

 developing themselves, so much so as to thrust aside the cells of 

 the Oscillatoria, and break through the thickened sheath of the 

 old filament, after which they passed into a filament like that of 

 (Edogo7iium ', but not being sure of the family of the Alga, I 

 waited for the determination of this, until chance favoured me 

 with the view of a filament not only extending along the sheath 

 of one of the Oscillatorice mentioned, but also bearing in addition 

 the peculiar spore of (Edogonium. Although in many of these 

 instances the cells of the Oscillatoria were dead, yet in several 

 the cells of (Edogonium were growing in the midst of the living 

 cells, and bursting through the sheath where the latter, from its 

 transparency and general appearance, bore no signs of previous 

 injury (PI. IX. fig. 15). 



Now here, neither the spore of (Edogonium nor its sporule 

 or gonidium can be supposed to have entered the sheath of the 

 Oscillatoria, as they, from their size, would probably have caused 

 such an injury of the sheath as would have led to the death or 

 rupture of the filament at this part. Hence we may infer, that 

 these cells arose from germs of extreme minuteness, which never- 

 theless had the power of penetrating the Oscillarian sheath. 

 May not the " globular vesicles ^' of the mucus-layer of Nitella 

 have been derived from germs of Rhizopoda equally small, but 

 endowed with a similar power ? Many small species of (Edo- 

 gonia, like Rhizopoda, have a great tendency to dwell on the 

 outside of the filamentous Algse; old filaments of Cladophora 

 are frequently covered with (Edogonium, and it seems not im- 

 probable that the minute germs of both Rhizopoda and (Edo- 

 gonium may have a like parasitic tendency, as well as power to 

 penetrate into their interior. 



Lastly, we have to consider how the germ, when so small, can 

 possess such power of penetration j a proposition which is easily 

 solved when we remember that almost every observation we 

 make on structural alteration in vitalized parts presents us with 

 an instance of bodies travelling from one part to another, or, in 

 other words, eff'ecting change of position by a solution of the 

 material which obstructs their progress. 



As, however, it is desirable to support this by a case in point, 

 or one as nearly allied as possible, I will cite a development 

 belonging to the class under consideration, which takes place in 

 the cells and resting-spores of Spirogyra. 



Just after the conjugation of Spirogyra, a number of spherical 

 Ann, ^ Mag. N. Hist. Ser. 2. Vol. xvii. 8 



