Dr "Barry on Tisaiparou^ Generation. 211 



importance, — an envelope raised for the operation in it of the 

 assimilative process which prepares the substance in its cavity 

 to undergo division. 



18. The following may serve as a rude sketch of this pro- 

 cess of assimilation, and of the generation of new cells to which 

 it leads. 



19. In the first place, the cell fills with minuter cells, the 

 germ of each of which is given off by the hyaline nucleus of 

 the parent cell ; which nucleus then appropriates to itself 

 the result of this cell- formation, — at the same time dividing 

 into two halves. 



20. More particularly, the process (as witnessed in the 

 ovum) appears to be as follows : — The cells, formed at the ex- 

 pense of the parent nucleus, are in concentric layers. The outer 

 or first formed layer liquefies, and the second layer enlarges by 

 imbibition and assimilation of the substance of the first. The 

 second layer in its turn undergoes liquefaction ; and now the 

 third, enlarging, receives and assimilates the already combined 

 substance of the first and second, and so on, — the assimilation 

 becoming more and more complete as it advances towards the 

 centre. 



21. This, however, is the merest outline ; for the cells in 

 the concentric layers are themselves filled with other cells, 

 which have arisen in the same manner, — in which the same 

 process is going on, — and the product of which is elaborated 

 by their parent cells ; the latter, again, being subordinate to 

 the first mentioned parent cell. (Par. 19). 



22. The result of this many-times-repeated process is, that 

 there is produced a mass of highly refractive globules of hya- 

 line, which are the essential parts — the hyaline nuclei — of as 

 many cells.* The mass requires only to be divided into two 

 halves ; a change effected by means of two cell-germs, into 

 which the nucleus of the original parent cell divides. These 

 two cell-germs have a central situation ; they imbibe the sur- 

 rounding pellucid assimilated substance — the hyaline — as a 

 sort of pabulum ; and, as they do so, become two cells, filled 

 with the hyaline of other cells ; and now the membrane of 

 the parent cell disappears. 



• Phil. Trans., 1840, Tlates XXIV., XXV., XXVI. 



