No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 309 



geneous, and a number of smaller globules, these latter stain- 

 ing as the former, and some of them containing vacuoles: " sie 

 stellen einerseits eine Zusammenballung der bisher ganz unre- 

 gelmassigen, im Keimblaschen vertheilten Chromatinsubstanz 

 dar, riihren andererseits aber wohl vom Keimfleck her." These 

 bodies have all disappeared in the ripe egg. 



Hubrecht ('87) noticed only a single nucleolus in the egg of 

 Ccrcbratuhis sp. ; as to the egg of Pclagoiietncrtes, he figures 

 one nucleus containing one large and several smaller nucleoli, 

 and another nucleus with only numerous small nucleoli. 



Kosinski ('87, '93, mentioned by Lavdowsky, '94) : within the 

 nucleolus of cancerous cells there is sometimes a vacuole, and 

 within the latter a small body which Kosinski considers may 

 correspond to Carnoy's " nucleoles-noyaux "; such nucleoli have 

 the faculty of division, and of wandering through the nuclear 

 membrane into the cytoplasm. 



Lukjanow ('87a), stomach epithelium of Amphibians : in the 

 cytoplasm of the cylinder epithelium are structures of various 

 form (" Nebenkerne "), which stain in general like the nucleoli. 

 In some of the nuclei of the deep layer of gland cells each 

 nucleolus is joined with a karyosome. 



Lukjanow ('87b) distinguishes three kinds of nucleoli in 

 muscle cells of Vertebrates: (i) " Plasmosomen "; (2) " Karyo- 

 somen"; (3) " Kernkorperchen von gemischtem Charakter." 

 The first stains deeply red (eosin), the second blue-violet (haema- 

 toxylin), while the third stains a mixed color with these two 

 stains (when used together). He remarks also: "dass in 

 manchen Kernen die Kernkorperchen ganzlich fehlen, in 

 anderen entweder nur eine Kategorie derselben, oder mehrere 

 zugleich vertreten sind. . . . Zuweilen liegt das Kernkorper- 

 chen sogar ganz ausserhalb des Kernes." 



Nussbaum ('8?) found in smaller eggs of Hydra a single large 

 nucleolus, while in larger ova several are present. " In frischem 

 Zustande sieht man in den allerersten Stadien neben den Keim- 

 flecken noch eine blasse Kugel, die im Gegensatz zu den Nucle- 

 olen des Keimblaschens keine Farbstoffe in sich aufnimmt." 



O. Schultze ('87) studied the maturation of the egg in Rana 

 and Triton. In the unripe germinal vesicle there are larger 



