498 MONTGOMERY. [Vol. XV. 



and finds that it has a closer chemical affinity to the substance 

 of the nuclear membrane (amphipyrenin) than to any other 

 substance. Judging merely from the reactions of these two 

 substances to stains I would agree in this point with Schwarz. 

 Zacharias ('82) shows also for plant cells that the nucleolar 

 substance is sid generis and is allied to plastin. O. Hertwig 

 ('92) terms the nucleolar substance " Paranuclein " and observes: 

 " Nuclein und Paranuclein betrachte ich als die wesentlichen 

 Substanzen des Kerns. . . . Beide scheinen mir in irgend 

 welchen Beziehungen zu einander zu stehen." But it is impor- 

 tant to note that the true nucleolar substance probably has no 

 chemical relation to the true chromatin (nuclein). Thus karyo- 

 somes should not be considered as a particular group of 

 nucleoli, since they are not nucleoli at all, but nodal points of 

 the chromatin reticulum. The substance of every true meta- 

 zoan nucleolus apparently differs chemically from the chromatin, 

 linin, paralinin, and oedematin (lanthanin) ; and accordingly 

 "pyrenin" is a term preferable to "paranuclein," though 

 " pyrenin " may include divers substances. 



There are also chemical differences between the nucleoli 

 proper (" Hauptnucleoli ") and the paranucleoli (" Nebennucle- 

 oli "), which occur together in many ova and in a few somatic 

 cells ; the substance of the paranucleoli stains more lightly 

 than that of the nucleoli proper. List ('96) distinguishes three 

 kinds of true nucleoli, from a chemical standpoint : (i) the 

 nucleolus of somatic cells ; (2) the nucleolus proper of germinal 

 vesicles ; and (3) the paranucleolus of germinal vesicles ; and 

 he considers the substance of the paranucleus of the germ cell 

 to be closer related chemically to the nucleolus of somatic cells 

 than either of them is to the nucleolus proper of ova. List 

 promises a more complete paper on this subject. The so-called 

 " nucleoli," which react like chromatin, are of course not true 

 nucleoli, but either karyoso7ncs (thickened nodal points of the 

 chromatin reticulum) or c/irovtatin nucleoli (independent lumps 

 or spheres of chromatin). It is my intention to devote a special 

 paper to the consideration of the latter structures. Other 

 papers on the chemistry : Macallum ('95), Michel ('96), Carnoy 

 and Lebrun ('97). 



