350 MOxXTGOMERY. [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 Tcstudo 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 fiir 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 Kiigelchen aufgehangt sind." 



Coe ('95), ova of Ccrebratulus lactcus : " 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 



