i86 NATURAL SCIENCE. Sept.. 



(3) NncUoles plasmatiqucs, the nucleoli proper. They contain no 

 nuclein, whatever else they may consist of, and they have, according 

 to Carnoy and Zacharias, a definite structure. 



A peculiarly interesting case is to be found in the nucleus of 

 Spho^yra. Here is a network winding through the nuclear space 

 which, from the small effect of the ordinary stains upon it, we 

 can conclude consists of linin with but few granules of nuclein 

 embedded in it. This latter substance appears to be aggregated into 

 one or two comparatively large spherules, which are usually spoken 

 of as " nucleoli." But since by the unqualified term we mean only 

 the nucleoli proper, the Nucleoles plasmatiques of Carnoy, the name is 

 evidently misapplied in the case of Spirogyra. The spherules are to 

 be spoken of according to Meunier (16) as Nucleoles noyaux, or, to 

 follow Moll and others (17 and 10), as Nucleoles nucleiiiiens, but not as 

 nucleoli simply. 



Such determinations as the above, in which we are guided by 

 morphological features and micro-chemical reactions, would be 

 greatly facilitated if we knew more of the part played by the true 

 nucleolus in the general physiology of the cell. As the case stands, 

 we know but little of the functions of the nucleus as a whole, and still 

 less of the duties of its component parts. With regard to the 

 nucleolus, opinions are most divergent. One body of observers main- 

 tains that it is merely a reservoir of food-material for the more vitally 

 active portions of the nucleus, whilst another group holds that it itself 

 takes a prominent part in the performance of the life-activities of the 

 cell. Strasburger, Carnoy, Pfitzner, and others, have all spoken for 

 the former view, while the names of Flemming, Zacharias, and Oscar 

 Hertwig may be mentioned among those who support the second 

 theory. 



The observations by Flemming (7), Biitschli (4), and Rosen (19) 

 of the frequent occurrence of vacuoles in the nucleolus may have some 

 bearing upon this point. Rosen, moreover, affirms that these vacuoles 

 are particularly abundant in plants, and that they are filled with 

 tannin. This, however, seems to be extremely doubtful. Many 

 careful examinations, notably those of Biittner (3), point to the entire 

 absence of tannins from the nucleus. 



In forming a distinction between nuclein-grains and nucleoli, 

 which are the two things most often confused, the safest guide we 

 can follow is the dissimilarity in their behaviour during cell-division ; 

 the nuclein bodies will be seen, upon the entrance into activity, to 

 break up into the chromosomes or nuclear-segments, while the 

 nucleolus will to all appearances vanish altogether, probably 

 becoming dissolved in the nuclear sap. A second datum of almost 

 equal importance, which must be taken into account in forming all 

 conclusions as to the nature of the nuclear structure observed, is its 

 behaviour with micro-chemical reagents. So difficult, however, is 

 the investigation of these minute parts of the nucleus that we cannot 



