No. 2.] COMPARATIVE CVTOLOGICAL STUDIES. 
undergoing a degeneration. Quite frequently a small spherical 
granule lies in the center of the nucleolus and this always 
stains more intensely than the surrounding substance (Figs. 
99-102). In only about half a dozen cases, out of hundreds of 
cells examined, did I find attached to the surface of the nucleo¬ 
lus one or two much smaller bodies, which also stained less 
intensely (Figs. 100 and 101). Can it be that in certain cases 
the nucleolus becomes differentiated into a “ Hauptnucleolus ” 
and a “ Nebennucleolus,” in which case these small bodies 
would represent the “ Nebennucleoli ” ? In certain of the cir- 
ratida of a young individual the nucleoli of the greater num¬ 
ber of nuclei were situated at that pole of the nucleus directed 
towards the median axis of the cirratidum, i.e. f those in the 
nuclei on the right side of the cirratidum were in the left-hand 
poles of the nuclei, and those in the nuclei of the left side of 
the cirratidum (as seen on sections) were placed at the right- 
hand poles of the nuclei. I did not observe this regular posi¬ 
tion of the nucleoli in the cirratida of the other individuals 
sectioned and hence would conclude that it was not a normal 
phenomenon, but an osmotic consequent of the fixing reagent. 1 
The size of the nucleolus preserves approximately the same 
ratio to that of the nucleus. 
The nucleus is either spherical or oval in outline. The 
apparent arrangement of the chromatin varies according to the 
fixative employed. After picro-nitro-osmic acid (Fig. 102) it 
appears granular; after Hermann’s fluid (Figs. 99-101), in the 
form of delicate fibers % which radiate from the nucleolus to the 
nuclear membrane; after alcoholic solution of corrosive subli¬ 
mate (Fig. 98) we find a few fiber's radiating from the surface 
of the nucleolus, but the greater amount of the chromatin 
appears in the form of granular masses, which lie mainly near 
1 In a previous paper (’ 96 ) I figured for the nuclei of those mesenchym cells 
which surround the distal end of the ventral nerve cords of Cerebratulus lacteus, 
the nuclei with their chromatic masses pressed against that side of the nuclear 
membrane which was situated nearest to the central point of the section. At 
that time, I regarded this excentric position of the chromatin as a normal but 
peculiar phenomenon; but now, on comparison with the cells of Doto, I am 
convinced that it is an artefact produced by the osmotic action of the fixing 
reagent. 
