April 1892.] THE BOTANICAL SOCIETY OF EDIXBURCH. 397 



this plasm which plays so important a part in the conjuga- 

 tion of cells, and how it does so I have represented in 

 figs. 50, a- (J. 



Describing simply the mechanism of conjugation, I believe 

 it to take place thus : — The endonucleolar fibrils running 

 through the body-plasm of the two sexual cells (in the centre 

 of the embryo-sac) are brought into contact with one another 

 whenever the pseudopodial processes of the two cells have 

 met. As soon as a union of fibrils has taken place, each 

 fibril will commence to contract similarly to a muscular 

 fibril, with the result that the two nuclei are gradu- 

 ally brought together ; that they become flattened off against 

 one another, because of the resisting nuclear membrane ; 

 that the nucleoli become flattened off because of the nucleolar 

 membrane, and that, ultimately, fusion of the two endo- 

 nucleolar plasms occurs. During this conjugation, in all proba- 

 bility, we have no " fusion " of analogous cell-elements of the 

 two conjugating cells, i.e., we have the individuality of the 

 corresponding organs, e.g., the chromatin-elements retained. 



If the view just stated be correct, that, namely, the endo- 

 nucleolar matter has the power of bringing cell-plasms, nuclei, 

 and nucleoli together, probably because of its intimate union 

 with these different organs, and because of its contractility, 

 and if the paranuclei (v. La Valette St George) are similar 

 in structure to the nuclei, i.e., if they too contain a plasm 

 corresponding to the endonucleolar plasm of the nuclei, and 

 if this plasm is permeating amongst other organs, also the 

 structures within the nuclear membrane, then many difficul- 

 ties could be explained, which I, without such a hypothesis, 

 cannot explain. 



Given then in a cell, firstly, a nucleus with a trophic 

 centre for the whole cell, namely, the endonucleolus ; and, 

 secondly, an extra-nuclear structure — the paranucleus — with 

 a trophic centre for the nucleus ; and, thirdly, an attachment 

 to or union of these two trophic-centre-filaments with the 

 various nuclear elements, then we could understand how, 

 in a resting-cell, the intra-nuclear centre may influence the 

 various cell-structures in such a way as to arrange them 

 concentrically round itself. 



Should, however, by any means the trophic influence of 

 the intra-nuclear centre be weakened, and a corresponding 



