No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 365 
mehrerer blauer Kiigelchen hervor. . . . Nach ihrem chemischen 
Verhalten stehen also Nebennucleolus und Nucleolus einander 
naher als Haupt- und Nebennucleolen ”; he concludes that the 
“Nucleolus” and the “Nebennucleolus . . . mindestens ver- 
schiedene Modificationsstufen des Paranucleins . . . darstellen.” 
Mytilus egg: what Lonnberg supposed to be vacuoles within 
the nucleoli, List holds are “ Nebennucleoli,” and these alone 
evince the characteristic Berlin-blue reaction ; by afterwards 
staining the preparation with carmine, “ die Masse des Haupt- 
nucleolus, das Nuclein, hatte sich scharf roth gefarbt, die 
Nebennucleolarsubstanz, das Paranuclein, rein blau.” Even in 
eggs where no yolk was as yet present, both these substances 
could be demonstrated. The “ Hauptnucleolus ” represents 
the greater part of the nucleolus, and is usually single ; in it 
may lie one spherical “ Nebennucleolus,” or the latter may 
cover, cap-like, one pole of the former; sometimes “Nebennucle¬ 
oli ” occur in the nuclear cavity, separated from the “ Haupt¬ 
nucleolus ”; occasionally there are true vacuoles within the 
latter. Pholas egg: (treatment with iron chloride, nitric 
acid, then “ Ferrocyankaliumlosung”) the “Nebennucleolus” 
is much larger than the “ Hauptnucleolus,” except in very 
small ova, where they may be equal in size. The last-named 
nucleolus may enclose a large, excentric vacuole, or in place 
of this, a “Nebennucleolus”; in the chromatin network of 
the nucleus there are small nodules of paranuclein, and some¬ 
times a free “Nebennucleolus.” “In alteren Eiern iiberwiegt 
bei Weitem der Nebennucleolus den Hauptnucleolus an Masse ”; 
the latter is either apposed to one end of the former, or there 
may be a large “Nebennucleolus” with a small “ Hauptnucle¬ 
olus ” at each end of it. Pristiurus egg : in the youngest 
germinal vesicles the minute nucleoli all lie at the nuclear 
periphery, the larger ones being central; in larger ova all the 
nucleoli are placed at the periphery of the nucleus. Sphaere- 
chinus egg : the supposed (Hacker, ’ 93 b) vacuole of the “Neben¬ 
nucleolus ” is in reality the “ Hauptnucleolus ”: “ Jedoch weichen 
meine Resultate von denen Hacker’s darin principiell ab, dass 
eben festgestellt werden konnte, dass das, was H. Hauptnucle¬ 
olus nennt, wie ein Nebennucleolus reagirt, und die Vacuole 
