M. Coste on the Formation of Cells. 381 
of organization, which, according to this theory, prepares the 
way for the cell-wall, of which all the anterior phenomena are 
indispensable precursors. 
Lastly, when the cytoblast or nucleus is formed around the 
nucleolus, and the total mass represented by their assemblage 
has assumed a certain volume, we find deposited on its ex- 
terior a new layer of substance, the fragile margins of which, at 
first vaguely defined, are soon consolidated and strengthened by 
the addition of new molecules. This more or less thin and de- 
licate mass, which is sometimes homogeneous and gelatinous, 
sometimes granular, is nothing more than the cellular wall which 
is developed on the surface of the cytoblast, as it were around a 
temporary frame-work, the presence of which becomes useless as 
soon as the structure which it supports is completed. 
But, when deposited around the cytoblast or nucleus, the new 
cell does not inclose this cytoblast in the centre of the cavity 
which it is about to circumscribe, as we should suppose ; on the 
contrary, it fixes it between the molecules which are about to 
form its generating wall, retains it inclosed amongst these mole- 
cules, and forms of it an integral part of the parietal membrane. 
This incorporation renders the cell-wall much thicker at that 
part which the cytoblast occupies than in any other part of its 
extent ; and it is for the purpose of expressing the appearances 
produced by this inequality of thickness, that the statement has 
arisen that the new cell resembled a watch-glass placed upon its 
dial. In this comparison, the watch-glass represents the thin 
and diaphanous portion of the wall; the dial corresponds to that 
part which the presence of the nucleus renders thicker ; and the 
space comprised between these two parts, which must be consi- 
dered as continuous, is intended to give an idea of the cellular 
cavity which is forming. 
When the new cell has acquired sufficient solidity, the per- 
sistence of an internal frame-work not bemg any longer neces- 
sary to support the strengthened walls, the cytoblast or the 
nucleus, attached to one point of the thickness of the parietal 
membrane, has no longer any part to play, and hence it should 
be atrophied and disappear. Then, in proportion as the cell en- 
larges, a peculiar liquid is introduced into its cavity and entirely 
fills it. This liquid, m which more or less abundant granulations 
may arise, forms the cell-contents, properly so called. But the 
cellular contents have nothing in common with the cytoblast or 
nucleus, and would in no case be required to fulfil the generating 
function which theory attributes to this same nucleus, since, ac- 
cording to this theory, the appearance of the cellular contents 
is always subsequent to the production of the parietal mem- 
brane. Now we shall show, in opposition to this view, that the 
