Animal and Vegetable Fibre. 321 



membrane. The membrane thus formed, or rather forming, 

 expands into the primary membrane of a cell, leaving the 

 nucleolus of the " cytoblast " to become the nucleus of the 

 cell.* 



The nucleus of the cell, too, has its pellucid centre or nucle- 

 olus, performing an office just the same as that of the nucleo- 

 lus in the "cytoblast." The nucleolus gives off globules. These 

 globules appropriate and assimilate the finely granular sub- 

 stance of the outer part of the nucleus into which they were 

 cast, and furnish the material out of which there is formed a 

 ring or coil of fibre. I saw the nucleus of the cell actually un- 

 winding itself as fibre ; and the fibre thus given off I followed 

 from the nucleus to the cell-wall, were it was either weaving 

 the secondary membranes, | or forming other deposits. 



Division of the cell is initiated by self-division of the nu- 

 cleolus. The nucleus, which had been the nucleolus, is found 

 divided into halves. J These two halves become two " cyto- 

 blasts," which undergo the same changes as the parent 

 " cytoblast." They become in the outer part coils of fibre. 

 These coils of fibre form the membranes of two young cells ; 

 and the walls of these two young cells where in contact with 

 one another produce a septum, dividing the parent cell into 

 two compartments ; and thus explaining division of the cell.§ 



The much disputed questions in vegetable physiology of 

 the mode of origin of secondary membranes, and division of 

 the cell, would have found a solution long before, had physio- 

 logists paid due attention to the nucleus of the cell, first re- 

 commended to especial notice by our illustrious fellow- 

 countryman, Robert Brown. One conclusion regarding the 

 nucleus they certainly did arrive at, but this was not until 

 after it had disappeared ; and then they agreed in concluding 



* For illustrative drawings in my paper " On Fibre," see those of many blood- 

 corpuscles ; for instance fig. 5, and other figures in Plate V. Some figures of 

 nervous substance in that paper also exhibit " cytoblasts," passing into coils of 

 fibre. 



t Loc. cit., Plate X., Fig. 133, from cartilage of the ear. 



X Loc. cit., Plate X., Fig. 134, from a neighbouring cell of the same cartilage. 



§ Loc. cit., Plate XL, Fig. 150. 

 VOL. LV. NO. CX. — OCTOBER 1853. X 



