266 Prof, H. Karsten on the Formation, 



its free surface, whereby the nucleus becomes involved in a 

 duplicature of the wall, or remains free, and is at length mostly 

 dissolved and lost to view. 



The majority of naturalists are now agreed that, in the vege- 

 table kingdom, free cell-formation from a more or less completely 

 organized nucleus of a mother cell takes place, but is of rarer 

 occurrence than the production of cells by fission, according to 

 the views of Mohl. 



In opposition to this hypothesis of a twofold type of cell- 

 formation, I sought, in 1843, in my dissertation 'De Cella 

 vitali,^ to establish the fact that the development of organic 

 forms is subject to one single law, to the recognition of which 

 the observation of the phenomena of development both of vege- 

 table and animal tissues had led me, and of the truth of which I 

 remain convinced now, after twenty years' study of this question, 

 alike important both for physiology and anatomy. 



Since that brochure is little known, and has been in some 

 I measure misunderstood, I will reproduce here those conclusions 

 which relate to the question under notice : — 



1. The formation of every cell within a living organism is 

 original: the cell is not divided into. two new individuals by 

 longitudinal or by transverse septa, or by proliferation. 3. The 

 evolution of a cell does not depend upon an antecedent forma- 

 tion of a solid nucleus. 3. In the first phase of its existence the 

 cell resembles a small vesicle, very like a mere point. 4. In the 

 organism the "cell of vegetation" does not exist in a simple form j 

 for everywhere a secondary cell is present. Every elementary 

 part of the organism (the cell is deemed elementary) consists of 

 a system of endogenous cells; a member which is sometimes 

 interpolated in this system of cells is the " cell of secretion." 



5. In the secondary cell a nucleus is found, which Schleiden 



called the formative cytoblast of the cell, but which I regard as 

 a small tertiary cell retarded in its evolution. 6. In the interior 

 of a cell one or several cells are developed with greater or less 

 rapidity, evidently in the same manner. 7. An organism poten- 

 tially consists of one such system of cells, i. e. a cell of reproduc- 

 tion ; actually of aggregated series, every one of which may be a 

 cell of reproduction ; never of a simple cell *. 



* 1. Omnis cellse formatio originaria est, intra vividum organismum; 

 cella dissepimentis longitudinalibus et transversalibus aut prolifera- 

 tione in duo nova individua non disjungitur. 



2, Cellae evolutio non pendet ab antecedente solidi nuclei formatione. 



3, In primo vitae suae gradu cella parva, puncto simillima vesicula ap- 



paret. 



4. In organismo non exstat cella vegetationis simplex ; ubique enim 



secundaria cella adest. Qusevis organismi pars elementaria (cella 

 q. d. elementaria) ex endogenarum cellwum serie constat ; mem- 



