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[Vol. XV. 
or two nucleoli. The nucleolus then wanders through the 
chromatin to take position in the center of the achromatic 
substance ; it combines the qualities of a true nucleolus with 
those of a centrosome. There is thus no fundamental differ¬ 
ence between a nucleolus and a centrosome ; when it remains 
in the nucleus it has the value of the former, when in the 
cytoplasm it has the significance of a centrosome. 
Bohmig (’95) noticed in the ovarial eggs of Haplodiscus that 
the nucleolus is at first small and homogeneous, while later it 
becomes larger, and one or more vacuoles appear in it. 
Bremer (’95a), blood cells of Testudo and Chelydra: there is 
normally one paranuclear corpuscle to a cell ; “ seiner Natur 
nach ist das Paranuclearkorperchen ein vom Innern des Kernes 
in das Diskoplasma [Cytoplasma] ausgewanderter Nucleolus 
oder vielleicht ein Nucleolusfragment, umgeben von einer dem 
Kerne entnommenen Hiillsubstanz. . . . Seine Grosse, die 
Schwierigkeit der Farbung und seine Lage sprechen fur den 
nucleolaren Charakter.” In a second paper (’95b) he identifies 
this corpuscle with a centrosome, and states : “ Hertwigs 
Vermuthung, dass ein Zusammenhang des Centrosoms mit dem 
Nucleolus existire, wird durch meine Beobachtungen wahr- 
scheinlicher gemacht.” 
In Burger’s monograph (’95) of the Nemerteans the following 
statement in regard to the structure of the germinal vesicle is 
of interest: “ Im Keimblaschen findet man ausser den intensiv 
farbbaren Korperchen, den Nucleolen, von denen meist zwei, 
ein grosseres und ein kleineres, vorhanden sind, ein Netzwerk 
feiner Faden, in welche sehr feine Kugelchen aufgehangt sind.” 
Coe (’95), ova of Cerebratulus lacteus: “ as the ovum 
increases in size its nucleus develops into the germinal vesicle 
which has many germinal spots, of which one or two are much 
larger than the others.” In the mature ovum the nucleus 
“often contains a highly refractive germinal spot one-third as 
large as the vesicle itself.” 
Cunningham (’95), ovarial eggs of fishes : in the youngest 
ova there is a single large nucleolus, in older ova a number of 
peripheral ones ; the latter are produced in part by a division 
of* the primitive nucleolus, in part by an increase in size of 
