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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 sui 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 yi 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 karyosomes (thickened nodal points of the 
chromatin reticulum) or chromatin 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). 
