4 Prof. H. Karsten on some Phenomena of 



tion ; on the other hand, their subsequent absorption has been 

 observed in various instances.) 



That a cell-nucleus is, as a rule, present in actively growing 

 cells, and that in withered cells or in those in a resting-state it 

 disappears, corroborates the statement derived from direct ob- 

 servation, that this nuclear cell possesses the property of deve- 

 lopment in itself. 



Indeed the constant absence of nuclear cells in the normally 

 detached cells of the epidermis of animals, and of the epithelium, 

 in the cells of the tissue in the tail of the tadpole, in the woody 

 cells of plants, &c., intimates the incapacity of such cells for 

 further regeneration and individual development. 



As only the resting-form of the nuclear cell in tissue- cells has 

 hitherto been recognized as the cell-nucleus, in many cases the 

 nucleus has been denied to exist where actually present and, in- 

 deed, in process of evolution, as, for instance, in tissues in con- 

 tinuous course of regeneration, e. g. in muscular tissue, the endo- 

 genous cells of which have at one time been considered nuclei, 

 at another cells. 



And it follows that, in cells which do not undergo regeneration 

 as lasting tissue-cells, nor self-multiplication, the nucleus is 

 always absent. Such cells are met with in those vesicles that 

 are produced in connexion with secretions, and are to be found 

 usually in large numbers in the fluid contents of genuine cell- 

 tissue. 



These generations of vesicles enclosed within a tissue-cell, and 

 often engaged in constant formation and transformation, are 

 the active instruments in the elaboration of organic material, 

 transforming the inorganic matters dissolved in the cell-juices 

 into combinations of a progressively higher grade. By means 

 of the assimilative properties possessed by these simple cells, 

 those substances are produced which either subserve the nutri- 

 tion of the still assimilating membrane of the parent cell, or, 

 where the cycle of its development is closed, are employed by 

 the nucleus in the regeneration of the life-energy of the cell. 



Moreover, when the individual development of the cell has 

 ended, and, together with the nuclear cell suppressed in its 

 revolution and destined to its regeneration, two or more new 

 daughter cells are formed and developed at the expense of the 

 parent cell, these secretory materials are employed for this pur- 

 pose ; and even after the formation of all such secondary ge- 

 nerations is brought to a close, they are transferred by exosmose 

 to other and remote parts of the organism to serve kindred 

 purposes. 



Some of these secretion-cells have walls so much thickened 

 {e. g. starch), or such opake and solid contents (e. g. chlorophyll). 



