34 Prof. H. Karsten on the Formation, — 
nuclei occur in the position usually occupied by them when the 
septum is half or completely lignified, although there is no trace 
of any such structure. In the middle between these two nuclei 
the third nucleus, belonging to the system of the mother cell, 
frequently occurs, all three enclosed within the very long and 
apparently nearly gelatinous membrane of their common mother 
cell (the original cell-nucleus), which is distinctly recognizable 
in a nearly round form in the conditions represented in figs. 
83 & 84. This elongated nuclear cell, with its three nuclei, is 
also apparently attached by mucoid filaments. 
This occurrence of several nuclei is to be explained by the 
deficiency of nitrogenous compounds in the water furnishing 
their nourishment, as appears from the phenomena of the deve- 
lopment of the septum, to be referred to immediately. 
In the so-called mucoid filaments which are so distinetly 
recognizable in many Spirogyre, as for example S. princeps 
(nitida and jugalis, Kg.), | have observed a movement proceed- 
ing slowly from the periphery towards the central nucleus, and 
this in individuals which had been lying for a short time in 
water containing carbonic acid, and also in the extremities of 
strongly vegetating plants. 
The mucoid filaments are therefore not solidified cords of 
plasma, excrescences from the membrane of the secondary cell, a 
framework for the support of the cell-nucleus floating in the 
middle of the cell, but a mucilaginous granular fluid, the true 
cell-juice, the fluid contents of the cell, in and from which the 
other cellular structures, both the nucleus and the vesicles con- 
taining secretion-materials, are developed. 
These fluid cell-contents certainly occupy the smallest part of 
the cavity of the cell, which is almost completely filled by the 
above-described colourless vesicles (p. 27) (fig. 72), so that they 
are limited, in the form of a fluid intercellular matter, to the 
spaces left between them by the latter in cells engaged in rapid 
vegetation. 
Schleiden saw this movement of the cell-juice in the extre- 
mities of Spirogyra, and supposed that the same took place in 
the mucoid filaments, in which it was subsequently observed by 
Nageli; Kiitzing, on the contrary, threw doubt upon it in both 
cases. 
The cause of this circulation of the juice of many vegetable 
cells is very probably to be found in the concurrent lively but 
chemically different assimilative energy of the membranes of these 
tissue-cells and of the secretion-cells (the so-called vacuoles) 
contained in them. 
That the latter are true cells, and not mere water-filled cavities 
of the mucilaginous cell-juice, I have already endeavoured to 
