494 REPRODUCTION BY SUBDIVISION. 



The commencement of cells is either, 1st, by self-origination, or, 2d, 

 by reproduction. 1st. Cells arise in an obscure manner from 



Origin of cells J r t n 



byseif-origina- homogeneous particles floating in a protoplasma, which, tak- 

 tion. j n g on Development, have a vesicle thrown over them, and, 



being of a spherical shape, present the aspect of a cell wall and cavity. 

 The granular content by degrees increases as the young cell grows in all 

 its dimensions. From that granular content new cells may arise. 



Though this process is spoken of as one of self-origination, it is quite 

 probable that the spherical and homogeneous particles floating in the 

 protoplasma, and which were the points of origin of the cells that have 

 arisen, were themselves nothing more than germs which had been pre- 

 pared by an antecedent generation of cells. This is the opinion com- 

 monly entertained of their nature, though its truth has never yet been 

 demonstrated by actual observation. It is adopted because of its proba- 

 bility, for we usually observe that every new organism is the descendant 

 of an older one ; yet it should not be forgotten that there must have been 

 a time when the first organic cell arose from inorganic material, and it is 

 not unphilosophical to suppose that what must have occurred once may 

 occur again. 



Origin of cells . 2d. Cells are reproduced from antecedent ones of the 

 by reproduction. same kind by subdivision, by budding, by endogenous gen- 

 eration. 



The reproduction of cells by subdivision is strikingly illustrated by 

 Reproduction theHasmatococcus binalis. The manner of the process seems 

 by subdivision. f b e as follows. The endochrome of the original spherical 



cell, , Fig. 230, begins to undergo bi-par- 

 tition as at b, and as the dividing portions 

 recede from one another the primordial utri- 

 cle bends round them. Next a layer of per- 

 manent ce ll wall, of a mucous character on 

 its exterior, is produced, which accompanies 

 the inflection of the primordial utricle as at 

 } e c, and, after a while, the bi-partition is com- 

 plete, and the separated portions constitute 

 distinct individual cells. The subdivision 

 may be repeated as at d. The seat of the 



Reproduction of H^matococcus binalis. primarv acti(m fe gaid to be in the endo _ 



chrome ; but of this there may be reasonable doubt, since generally the 

 primordial utricle is the place of energy of the cell ; and where nucleated 

 cells undergo multiplication by this process of fissure, the nucleus di- 

 vides along with the endochrome, so that both the resulting portions pos- 

 sess a part of it. But if the utricle, with its nucleus, was inert during 

 this operation, it would seem that the vesicle should tear any where 



