April 1892.] THE BOTANICAL SOCIETY OF EDINBURGH. 387 



three parts are separated from one another by the nuclear 

 (3) and nucleolar (5) membranes, membranes which are, as 

 has already been pointed out, probably the inner denser areas 

 of the body-plasm and nuclear plasm respectively, and which 

 do not correspond to the outer denser parts of the nucleolus 

 and nucleus. 



In the same fig. 48, two sets of strands or fibrils have 

 been represented, one set as dark lines radiating from the 

 centre of the nucleolus, i.e., from the central endonucleolus 

 (a) ; and a second set as dotted lines radiating from two 

 paranuclei (?») just outside the nuclear membrane. 



Let us study next the endonucleolar plasm more minutely 

 (fig. 48). 



In a resting cell, i.e., a cell not about to undergo either 

 division or conjugation, the centre of the nucleolus is occu- 

 pied by a large endonucleolus (a), which sends out minute 

 fibrils (c) through the nucleolar substance (6). Each fibril 

 has a proximal (b) and a distal (d) swelling, and the proxi- 

 mal swellings of the various fibrils form conjointly a corona 

 surrounding the central endonucleolus, while the distal 

 swellings give rise to a light area just internal to the 

 nucleolar membrane. From the distal enlargements the 

 endonucleolar fibrils pass through the peripheral nucleolar 

 area, and then through the nucleolar membrane into the 

 nuclear achromatin.* Here they may be recognised, as 

 they possess a lower refractive index than the turpentine- 

 balsam. 



On turning to fig. 45 we find a large number of pores in 

 the nuclear membrane, most of which differ, however, from 

 the nucleolar pores in being much larger (p. a), a fact which 

 could be accounted for in several ways, either the endo- 

 nucleolar fibrils (which I have represented as passing 

 through the nuclear membrane in fig. 48) receive an enve- 

 lope of nuclear achromatin, or the endonucleolar fibrils 

 undergo an increase in thickness in the nuclear area, or 

 perhaps the larger pores in the nuclear membrane (figs. 45, 

 46) are for the transmission of structures other than endo- 

 nucleolar ones, structures which may pass either from the 

 cell-plasm to the nucleus or in the opposite direction. In this 



* Synonyms : Kernsaft (0. Hertwig) ; Zwischensubstanz, Achromatin 

 (Flemming) ; Karyochylema (Strasburger) ; Paralinin (Waldeyer). 



