Structure and Division of the Vegetable Cell. 201 



teasing and rolling witli a needle handle, so as thoroughly 

 to set free all loose protoplasmic material, it will still be 

 found that many of the nuclei remain, though broken up, a 

 fibrous network being still discernible, and, what is note- 

 worthy, the nucleoli almost invariably are present as if 

 moored to the nucleus in a definite way. 



I would now notice the results at which Flemming has 

 arrived in studying the animal cell. In a paper published 

 in 1879 * he considers that two forms of division have been 

 described — the direct and indirect. In the former, " sup- 

 posed until recently to be the normal one, the nucleolus 

 first divides, then the nucleus, and finally the cell. In the 

 indirect method, the nucleus, first of all, undergoes meta- 

 morphosis, separating into a network of highly-refracting 

 filaments, and an intermediate substance not affected by 

 staining fluids. The nuclear network goes through a 

 definite series of changes, and finally divides," f these masses 

 then representing the two daughter nuclei. Flemming at 

 that time did not believe that direct division ever took 

 place. In a more recent paper % he is inclined to suppose 

 that both kinds of division may occur, though the indirect, 

 in his estimation, is by far the commoner. In using these 

 terms he regards them merely as provisional. He further, 

 after describing most carefully the metamorphosis which 

 the nuclear fibres undergo, comes to the conclusion that 

 forces seated in the achromatic, or the nuclear substance 

 component, of the nucleus, are the real initiators and 

 directors of division. But he then propounds the thesis 

 that the function of the nucleoli has in this respect been 

 greatly mistaken, since he supposes that better methods 

 may show that they are not even morphological con- 

 stituents, but mere thickenings or deposits. It has been 

 my aim to show that it is neither the plan of direct or 

 indirect division, so called, that goes on, but a process 

 compounded of the two, and requiring both of these sup- 

 posed distinct ones to explain it. Moreover, Flemming 

 himself very beautifully suggests that, to account for the 

 peculiar changes of the nuclear fibres, we require only two 



* Archiv Path. Anat. u. Phys. (Yircho-w) Ixxvii. 1879, p. 181. 

 t Abstract Roy. Micro. Journ. vol. iii. 1880, p. 51. 

 I Arch, fiir Mikr. Anat. xviii. 



