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substances when they dry up in the air.” * But, unfortunately, 
this explanation, although undoubtedly more in consonance 
with the facts as regards the colourless protoplasm, is based on 
the assumption that there is no kind of dividing film inte- 
riorly to the cellulose wall ; and, consequently, that the true 
endochrome is not separated in any way from the colourless 
formative layer which is an invariable and most important con- 
stituent of the general cell contents. 
Again, since distinct apertures are known to exist in the 
cellulose wall of the Desmid, and the siliceous covering of the 
Diatom, occurring sometimes as mere minute perforations, 
sometimes as projecting processes which are distinctly tubular, 
it is reasonable to conclude that these channels of communica- 
tion between the exterior and the interior parts serve the pur- 
pose of bringing the protoplasmic substance into immediate 
contact with the medium in which the organisms live, and from 
which are derived all the materials for their development and 
growth. And coupling these facts with the indisputable pre- 
sence, in a large number of the Desmidiacese and Diato- 
macese, of a jelly-like secretion, altogether externally to the 
cellulose and siliceous walls of these organisms, and the diffi- 
culty of explaining how this jelly-like secretion is either pro- 
duced or kept in “ working order ” otherwise than through 
being in direct communication with the colourless formative 
layer through the intervention of the apertures in the pro- 
tective wall, it appears almost impossible to doubt that the 
quasi - vitality of the gelatinous secretion (or exudation, if this 
term be preferred) is determinable only by the death of the 
parent structure. 
As the evidence furnished by Glosterium is of a very im- 
portant kind, it is right to mention that the drawings from 
which the accompanying figures were copied were made from 
nature ; that no chemical reagents were employed to render 
the true characters more pronounced, solely in order to avoid 
the risk of at the same time evoking characters that are facti- 
tious ; and that the specimen depicted at B, fig. 2, was but 
one of many similarly crushed, whilst under observation on the 
stage of the microscope, to show the relation between the cell 
wall and the several cell contents. 
Prior to the application of pressure, the frond (fig. 2, a) pre- 
sented the following characters. Immediately within the well- 
defined cellulose wall, a, and completely investing its inner 
surface, was to be seen the thin stratum of amorphous colour- 
less protoplasm, sharply divided on its inner aspect from the 
masses of brilliant green protoplasm constituting the true endo- 
* u Micrographic Dictionary ” Third Edition, p. 643. 
