April 1892.] THE BOTANICAL SOCIETY OF EDINBURGH. 391 



highest importance, and specially in combination with the 

 other fact that the paranuclei have a nuclear origin, as 

 pointed out above, and as also believed by Hermann, who, 

 in the same paper, p. 88, states that the paranucleus is, in 

 all probability, derived from the interior of the nucleus as an 

 originally non-stainable body. These various facts seem to 

 justify us in considering the paranuclei as diminutive nuclei. 

 Amongst botanists, Guignard * pointed out the presence of 

 paranuclei, or, as he calls them, " attractive or directing 

 spheres," in vegetable tissues, c.rj., in the primordial mother- 

 cells of the pollen of Lilium, Listcra, Ncvias, and in the 

 mother-cell of the embryo- sac, and confirms the observa- 

 tions of zoologists as to the part they play in cell division. 

 Wildeman t confirms Guignard's observations, and states 

 that very typical paranuclei are found in B'pirogtjra nitida, 

 and that they also occur in the mother-cells of the spores of 

 Anthoceros Icevis and Isoetes Burieui, further in Funaria 

 hygromctrica, Ceratodon purpurcus, and Bryum ccespitosum. 

 Van Tieghem | proposes to call the paranuclei the " directing 

 leucites," or tinoleucites. 



What is Known about the Functions of the Nucleus, 

 THE Nucleolus, and Endonucleolus ? 



To attribute to these organs the " functions " of fertilisa- 

 tion and division is impossible, as both fertilisation and 

 division must be regarded only as phenomena in the life- 

 cycle of a cell, determined by factors injurious to the main- 

 tenance of the individuality of each cell. To put it 

 differently : — 



Each cell once formed will endeavour to develop and to 

 retain its individuality as long as extrinsic and intrinsic 

 agencies will allow it to do so. Should, however, the 

 equilibrium existing between the various organs of a cell 

 be upset, an equilibrium necessary for the normal fulfilment 

 of the different physiological functions, then, if the cell be 

 not killed outright, a tendency to restore the disturbed 

 equilibrium may lead, on the one hand, to the division of 

 a cell, or, on the other hand, to the conjugation of two 



* Comptes Rend., cxii. (1891), pp. 539-42. 



t E. De Wildeman, iu Bull. Acad. Roy. Sci. Belgiqiie,lxi.(1891), pp. 594-602. 



t P. Van Tieghem, in Journ. de Bot. (Morot) v. (1891), pp. 101-2. 



