108 VEGETABLE CELLS. 



These forms with two, three, or four nucleoli seem to prove 

 that the nucleus generally originates before the nucleoli. 

 Since no distinction is evident in the nucleoli, one is in- 

 clined to regard them all of equal value ; and since some 

 of these nucleoli certainly originated after the nucleus, 

 one is led to assume the same of all. I believe, how- 

 ever, the assumption that one of these nucleoli originated 

 before the nucleus and produced it, and that the rest were 

 formed subsequently, may be warranted by the analogy 

 with cells. In cells also we sometimes find several nuclei, 

 a primary and one or two secondary nuclei.* Therefore, 

 since both the life of the nucleus with the life of the cell, 

 and the relation of the nucleolus to the nucleus with that 

 of the nucleus to the cell, exhibit so great analogy, we 

 may reasonably assume, that when a nucleus contains 

 several nucleoli, one of them is the primary, which ori- 

 ginated prior to the nucleus, while the rest are secondary 

 nucleoli formed within the nucleus. 



The nuclei have now attained a definite magnitude. 

 Their membrane may sometimes be seen indistinctly on 

 their periphery. Their mucilaginous contents are either 

 homogeneous or very slightly granular, of variable density. 

 The substance of the nucleoli is generally denser than that 

 of the nuclei, sometimes of equal, at others of a less, de- 

 gree of density, so that in the last case the nucleoli appear 

 as clearer spaces in the denser contents of the nuclear 

 vesicle. 



Subsequent stages exhibit nuclei, like those just de- 

 scribed, with a thin layer of homogeneous mucilage. This 

 layer is usually much thinner on one side than on the 

 opposite (fig. 8, d). More rarely it is equally thick on 

 all sides ; which may be ascertained from the fact, that, in 

 rolling, the nucleus always retains its central position (fig. 

 8, e). The mucilage is perfectly homogeneous, distinctly 

 defined externally, and bounded by a somewhat darker 

 line. As yet I can discover no membrane. The mucilage 



* See Part I of this Essay. Ray Society's Translation, pp. 242 et seq., 

 and pp. 247 et seq. 



