244 
PEOCEEDINGS OP SOCIETIES. 
stance which attracts notice, in addition to the remarkable length of the 
cells, is the presence of a narrow pale band, or interruption of the en- 
dochrome at the centre of each joint, which fact appears to me sufficiently 
significant to indicate that towards the Desmidiaceae we are to look for 
its affinities. I will try briefly to describe a joint more closely. Each 
joint in proportion to its breadth is extremely long, sometimes, though 
rarely, as many as forty times, averaging, perhaps, from twenty to thirty 
times longer than broad, and it is nearly cylindrical and quite smooth. (See 
Plate XXI., Eig. 1.) There are two points of view from which a diffe¬ 
rent aspect of the cell-contents is obtained, from the fact of the endochrome 
being disposed in a longitudinally compressed or flattened band. When 
the broader diameter of the endochrome is towards the observer, it is seen 
to fill the entire width of the cell, and having, as before adverted to, a 
narrow, transverse, pale space at the centre (separating the endochrome 
into two equal portions), sometimes band-like, but more frequently cir¬ 
cular, from the endochrome terminating at each side with a concave out¬ 
line. There is a single central longitudinal series of “vesicles” (or 
bodies similar to those in Closterium, &c.), reaching from end to end of 
the endochrome, and disposed at intervals of somewhere about the dia¬ 
meter of the joint, one of these always occupying the centre of the pale 
space. The bodies which, following the name used by Ralfs for similar 
appearances in Closterium, &c., I have just called “vesicles,” I believe 
are not truly vesicles , but solid bodies, or corpuscles. Pressure upon the 
joints obliterates, or rather hides them, causing the endochrome, which 
before was apparently of an uniform character, to assume a granular ap¬ 
pearance ; while a still greater force upon the pressed-out cell-contents, 
now become somewhat scattered-about, shows these globular bodies, per¬ 
haps some not much altered, others cracked or split, and others in frag¬ 
ments (Eig. 4). If these were truly “vesicles,” or if they were vacuoles, 
I do not think this appearance could result. Were they vesicles, I ap¬ 
prehend that, by careful manipulation, they should be capable of being 
pressed out either in a collapsed or burst state. Were they vacuoles, I 
should imagine that pressure would only efface them, and that they 
would hardly be found in the mass of extruded endochrome, whereas in 
reality pressure cracks and breaks them, as before stated, into fragments. 
I think, then, that the endochrome is at first of a very finely granular na¬ 
ture, so as to appear homogeneous, oruniform, whenfresh, with this median 
series of firm corpuscles imbedded, which are spherical, and of a smooth 
and well-defined outline. They are, I should think, granules of chloro¬ 
phyll, of a firmer texture, but of a lighter colour, than the remaining 
endochrome. That they might occasionally contain starch is, I suppose, 
probable. I tried the application of iodine, but without being able to 
see the characteristic tint of starch,—the whole plant being stained a 
yellowish-brown, while the central corpuscles became very much darker 
than the other part of the endochrome. At each extremity of the joint 
the endochrome becomes more or less retracted from the end of the “ pri¬ 
mordial utricle,” leaving a clear space, which, in cells just after division, 
is very small, but which afterwards becomes greatly larger. Within 
