No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
3 21 
a smaller mass of chromatin, or at least of a substance which 
does not differ in its reactions from the chromatin of the coiled 
filaments in the same nuclei.” This nucleolus divides first 
in mitosis. 
1890. 
Auerbach (’90) distinguished two kinds of chromatin sub¬ 
stance : “ erythrophile,” i.e., substances staining with eosin, 
fuchsine, aurantia, carmine, picrocarmine; and “ kyanophile,” 
substances staining with methyl green, aniline blue, haematoxy- 
lin. The nuclear reticulum is not the fundamental portion of 
the nucleus, but the nucleoli are its important elements. He 
finds “ dass in einer Grundsubstanz, die im frischen Zustande 
homophan, im geharteten . . . hochstens feinkornig erscheint, 
grossere, scharf begrenzte, isolirte, starker lichtbrechende und 
starker farbbare Korperchen, Nucleoli, von wechselnder,aber fur 
die verschiedenen Zellarten und Thierspecies typischer Anzahl 
eingebettet sind”; thus in the Batrachia most of the nuclei 
contain numerous nucleoli, and when they are particularly 
abundant the greater number are peripheral in position. 
There are two kinds of “ Kernkorperchen,” those which stain 
blue (or green) and those which stain red (or yellow) ; both 
kinds occur in most nuclei. In the giant nuclei of the gland 
cells from the skin of Urodelea are found ( 1 ) numerous small cyan- 
ophilic nucleoli, and ( 2 ) from one to fifteen (usually two to five) 
much larger, erythrophilic nucleoli, which sometimes contain vac¬ 
uoles. Embryonal nuclei contain only cyanophilic nucleoli, while 
in maturer nuclei erythrophilic nuclei become differentiated 
from the former. Thus in the blood corpuscles of frog larvae 
there is at first only one large nucleolus, which later differenti¬ 
ates into an inner erythrophilic and an outer cyanophilic por¬ 
tion. The peripheral layer next breaks up and divides into 
small cyanophilic nucleoli, while the central portion remains 
as a large erythrophilic nucleolus. Subsequently the smaller 
cyanophilic nucleoli (“ Nebenkiigelchen ”) may fuse together 
so as to produce six or eight larger cyanophilic nucleoli, each 
of which attains the size of the original “ Stamm-Nucleolus ”; 
at the conclusion of the larval period of the frog, the latter 
