Development, and Structure of the Vegetable Cell, 281 
normally developed and well-nourished cell, are for the most 
part not perceptible externally, and which originate by the growth 
of small yellowish-coloured vesicles, very similar to those of 
chlorophyll in their earliest stage. In many cases also it may 
be distinctly seen that a starch-corpuscle occupies the position 
of a nucleus within mature chlorophyll-vesicles. 
Bary’s idea that chlorophyll occurs in the external layer, and 
starch more in the interior of the joint-cell, will not, therefore, 
hold good. Indeed, in my researches on Vaucheria (Botan. 
Zeitung, 1852), I showed that in that plant the starch was usually 
to be found towards the exterior of the cells that contained 
chlorophyll. The same obtains in GZdogonium, in those cells in 
which new joint-cells have originated. The large, much-thick- 
ened starch-corpuscles, when chlorophyll is not present with 
them, are met with external to the cells which contain chloro- 
phyll as well as delicately walled starch-vesicles. The explanation 
of this relation is to be found in the successive development of 
new endogenous cells within the joint-cell of the Gidogonium. 
As the phases of development of neighbouring joint-cells of 
(Edogonium differ very much from each other, so also do the 
joint-cells often present very different conditions in regard to 
the distribution of the secretory materials contained within 
them. 
The true nature of the functions of the nuclear cell (nucleus) 
in relation to cell-formation in general, as well as to the multi- 
plication of cells, in the case of Cdogonium, has not been 
rightly understood. A cell-nucleus is frequently absent from 
the cells of Gtdogonium during the formation of new cells— 
probably, indeed, more frequently absent than present; and 
without doubt its existence, or rather its form, is dependent on 
the conditions of nutrition and on the chemical composition of 
the plasma. Besides, where the nucleus is present, it can be 
shown that the origin of new cells, and still more the formation 
of a septum, is quite independent of it. 
In those cells wherein a nucleus of the ordinary form exists 
at the time of the formation of new cells, it is found to lie often 
on the wall of the mother cell (fig. 28), often in the median line, 
sometimes at its centre, and at others nearer to one end; and, 
in the course of the growth of the daughter cells, which do not 
- originate in‘ contiguity with it, it becomes thrust to one side 
along with the other contents, and pressed against the inner 
wall of the mother cell. In this position it immediately begins 
to undergo absorption—a process which scems to be frequently 
preceded by a swelling-up of the nucleus. Mostly this act of 
absorption is speedily completed; and then only does a nucleus 
make its appearance in each of the two new joint-cells, hitherto 
Ann. & Mag. N. Hist. Ser.3, Vol. xiii. 19 
