UKJUVENESCENCE IN NATURE. 173 



imagined by Areschoug* to be the rudiments of the active 

 germ-cells. When the cells are less perfectly developed, 

 the internal mucilaginous layer exhibits a reticulated ap- 

 pearance, forming very irregular green meshes on a yellow 

 ground. Whether, in this case, these are real reticu- 

 lated perforations, or the chlorophyll merely is contracted 

 withia a continuous mucilaginous layer, I shall leave 

 undecided. I mention this reticulated structure in order 

 to observe, that although it vanishes subsequently on the 

 more vigorous development of the cells, it is a normal 

 occurrence in the young cells, and commences even on 

 the first day of existence, by the green contents, originally 

 uniformly filling up the cell, contracting into a broad green 

 zone, which divides more and more in the succeeding 

 days, and so gradually passes into the formation of a 

 many-meshed net, a phenomenon which at the same time 

 indicates that the separation of the contents into the 

 various layers occurs in the very earliest youth of the cell . 



4. The fluid, which fills up the interior of the three- 

 fold sac. It is of watery consistence, and no further 

 organic parts can be distinguished in it. 



Thus, then, it is shown that the cell-contents form a 

 far more perfectly organised body than is ordinarily 

 imagined ; that they exhibit a multiplicity of differences 

 of organisation, which are no less important than the 

 difiierences of the cell-membrane, to which vegetable 

 anatomists have hitherto almost exclusively paid attention, 

 and which after all may themselves be merely results of 

 special peculiarities of the contents. As the modifications 

 of the structure of the cell-wall have been used, not only 

 for the distinction of the difierent kinds of tissue, but 

 even for the characterisation of the great divisions of the 

 Vegetable kingdom, so must the differences of the organi- 

 sation of the cell-contents, which have hitherto found 



* Areschoug, 'De Hydrodiotyo Utriculato,' 'Dissert. Bot.,' Lundae, 

 1839, Liunsea, 1842, and Hassall's ' Presh-water Algae,' 225. 



