382 M. Coste on the Formation of Cells. 
cellular contents, in a great number of cases, have a direct in- 
fluence, and that the vesicle which incloses them is generally 
developed around them. 
Finally, when the phases of a first generation are accomplished, 
new cells are formed in the cellular contents by the same me- 
chanism by which the maternal cells are developed from the pri- 
mitive cytoblast. In this manner, by an incessantly-renewed re- 
petition of the same phenomenon, the organic tissues, according 
to this theory, prepare the materials of their growth and multi- 
plication. 
Such is the theory, deprived of the vagueness and the obscu- 
rities which manifestly arise from the uncertainties which a defi- 
ciency of precise observations leaves in the minds of its authors ; 
such is the theory which it is proposed to elevate to the rank of 
a universal principle. Let us see how far an attentive exami- 
nation of the facts will authorize the pretensions of such a doc- 
trine. The fundamental character of this doctrine consists, as 
we have seen, in the succession of four distinct periods, of which 
the evolution of each cell should always consist. 
The first is represented by the appearance of the nucleolus, 
which is the basis of the structure, and itself results from a 
simple agglomeration of the molecules of the cytoblastema. 
The second corresponds to the deposit and to the coagulation 
of the cytoblast or nucleus around the nucleolus, considered as 
the unique and exclusive centre of all cell-formation. 
The third, to the deposition and coagulation of the cell-wall 
around the cytoblast, which it grasps at one point of its sub- 
stance, and on one side of which it appears at first applied hke a 
watch-glass upon its frame. 
The fourth is expressed by the absorption of the nucleus and 
by the admission of cellular contents, which, being subsequently 
introduced, cannot consequently have taken any part in the for- 
mation of the parietal membrane. 
Now if this is the sole mechanism by means of which all 
organic cells are developed,—if it be true that the four funda- 
mental modifications which prepare the way for thei walls are 
always produced in the order of succession which we have 
pointed out, it should result that wherever there are cells in the 
course of formation,—the cytoblastema should present in the 
metamorphoses of its substance, each of the material modifica- 
tions which constitute the terms of this essential succession. If 
then the theory is to aspire to the rank of a general doctrine, it 
will be necessary that in the self-organizing mucus we should 
always be able to meet with the free nucleolus, the nucleolus in- 
closed by the cytoblast, the cytoblast at the moment at which 
the cell-wall is deposited on its periphery; and finally the cyto- 
