EEJUVENESCENCE IN NATURK. 165 



of M'hich girdle the internal cavity as green zones, in each 

 cell. In the median line of these zones are found, as in 

 the spiral bands of Spirogyra, starch-vesicles, from five 

 to seven in each ring; the surface of the rings, moreover, 

 appears spotted with very fine granules, and the margins 

 irregularly denticulated. The outer surface of the zones 

 lies flat upon the cell-wall, the inner surface projects with 

 a strong " keel" into the cavity. The whole series of 

 zones are connected together by a delicate, colourless, 

 mucilaginous layer or primordial membrane, which lines 

 the whole of the internal surface of the cell-membrane, 

 and which is traversed by extremely delicate lines and 

 branched and anastomosing green longitudinal streaks 

 issuing from the teeth of the zones. But the strangest 

 peculiarity of the conformation of the cell-contents of 

 Sphceroplea lies in the chambering which occurs in them. 

 Each zone supports a delicate, colourless diaphragm, 

 arising from the annular keel or ridge, and stretched 

 across the cavity of the cell. These septa, which convert 

 the cavity of the cell into a many- chambered tube, have 

 no association at all with the external cell-membrane, 

 they are merely connected with the mucilaginous layer, 

 and formed of the same substance as this. I have had 

 no opportunity of tracing the origin of these chambers, 

 as I have never been able to find Sphceroplea in a suffi- 

 ciently young state ; but it can scarcely be doubted that 

 their presence and arrangement is to be explained by the 

 production of a row of water-bubbles in the originally 

 homogeneous contents (protoplasm) of the cell, which 

 idea is borne out by the not unfrequent occurrence of 

 larger and smaller intermediate vesicles lying in the zones 

 themselves. The whole of this artfully arranged struc- 

 ture of cell-contents collapses as soon as the fructification 

 commences. First the zones become" somewhat detached 

 from the cell-membrane, so that the internal tube appears 

 constricted by bands and articulated ; then the primordial 

 utricle, with the septa, vanishes altogether, the green zones 



