M. Coste on the Formation of Cells. 8&1 



of organization, which, according to this theory, prepares the 

 way for the cell-wall, of which all the anterior phsenomena 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 being 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, in 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 



