THE CELL DOCTRINE. 47 



that the segments into which the egg breaks tip are 

 cells. Karsten* (1843), published a dissertation upon 

 the cell, in which he stated that cells originate with- 

 out a pre-existing nucleus, and by the expansion of 

 anaorphous granules of organic matter; and more 

 recently (1863), the same author practically reiterates 

 this view, since he says that all " cells of vegetables 

 originate as minute free vesicles in the •fluid contents 

 of previously existing cells," and regards the nucleus 

 as a "small tertiary cell, retarded in its develop- 

 ment."t Again, " when the nucleus is present, the 

 origin of new cells is quite independent of \i"X In 

 addition to the statement already given, Henle also 

 (1843), alleged that some of the so-called fibrous tis- 

 sues were " formed by the aggregation of granules 

 in a certain wa-y without the intervention of true 

 nucleated cells."§ Kolliker,|| one of the foremost 

 exponents of the cell doctrine of the present day, in 

 1844 expressed his dissent from the idea of unity in 

 the mode of cell formation, and states that if there 

 is a single method of cell formation which is in- 

 variable, it remains to be discovered, although he 

 interpreted the segmentation of the germ of ce- 

 phalopods in the same manner as Bergmann. Mr. 



* Karsten, De Cella vitaie Dissertatio. Berlin, 1843. 



f Karsten, Ann. and Mag. of Nat. History, vol. xiii, p. 268. 

 London, 1864. 



X Karsten, Ann. and Mag. Nat. History, vol. xiii, p. 281. 



g Henle, Traite d'Anatomie G^nerale. Trad. d'Allemand, 

 par A. J., Jourdan, 2 vol., Paris, 1843, torn. 1, p. 374. 



II Kolliker, EntwickelungsgeschichtederCephalapoden. Zurich, 

 1844. 



