aes peti sociean 
ue eee 
. . Zoology. 281 
Ill. Zoonocy. 
1. On the Formation of Cells; by M. Coste, (Ann. Mag. Nat. 
Hist., xvi, 377, from Comptes Rendus, Oct. 20, 1845.)—The prevalent 
view with regard to the formation of cells, is a generalization of Pur- 
kinje’s theory upon the development of the egg in the ovary. Its fun- 
damental character consists in the supposed existence of four succes- 
sive periods or phases in their development. 
The first is represented by the appearance of the pssleitens which 
is the basis of the structure, and itself results from a simple agglome- 
ration 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 substance, and on one 
side of which it appears at first applied like 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 formation of the parie- 
tal membrane. 
Now if this is the sole mechanism by means of which all organic 
cells are developed,—if it be true that the four fundamental modifica- 
tions which prepare the way for their 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 ma- 
terial modifications which constitute the terms of this essential succes- 
sion. 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 enclosed by the 
cytoblast, the cytoblast at the moment at which the cell-wall is deposit- 
ed on its periphery ; and finally the cytoblast, enclosed in the thick- 
ness of the parietal membrane, disappearing in proportion as the cell 
contents are introduced into the cavity of the latter. 
But when we search for the facts upon which so radically exclusive 
a theory is founded, we experience the twofold astonishment of not 
meeting, in those authors who originated it, with a single example, the 
value of which we cannot seriously contest, and of not finding in na- 
ture those abundant proofs which cause a system to prevail, or at least 
allow the formula to remain, as the most faithful expression of the most 
humerous category. Thus, in examining the proofs cited by Schwann 
Seconp Srrizs, Vol. I, No. 2.—March, 1846. 
