No. 2.] COMPARATIl'E CYTOLOGICAL STUDIES. 363 



together with the nucleoli correspond to the macronucleus of 

 the Infusoria. 



Gerould ('96), ovarial eggs of Caudina : in the youngest ova 

 there are numerous peripheral nucleoli ; these increase in size 

 as the nucleus grows, and subsequently each contains a vacuole, 

 but they are always close to the nuclear membrane. 



Greenwood ('96), macronucleus of Carchesiuni polyphmvi : 

 the nucleoli (" protomacrosomes," in distinction to the " pro- 

 tomicrosomes," or chromatin granules) are numerous and 

 vacuolated, and stain like true metazoan nucleoli. They vary 

 in size and form, and are probably amoeboid, though this point 

 could not be determined in the living nucleus, which is first 

 rendered visible by reagents. The vacuoles are fiuid accumula- 

 tions, and arise first in the center of the nucleolus. " No 

 vacuoles surround the macrosomes of Carchesiuni at any time, 

 nor do they ever show general increase of fluidity or swelling 

 such as might accompany the penetration through them of some 

 secretion from without ; . . . the deposition of vacuolar fluid is 

 centrifugal ; . . . thus the macrosome may become a bladder- 

 like or honey-combed structure, its residual solid (.■') forming a 

 well-defined membrane-like investment for fluid contents." 



Henneguy ('96) distinguishes true and false nucleoli (the 

 latter being " noeuds du reseau," in the sense of O. Hertwig, 

 '92). He reviews the observations upon nucleoli made by 

 several previous authors. 



R. Hertwig ('96), unfecundated ova of echinoderms poisoned 

 with strychnine : the nucleoli vanish within the nucleus as the 

 chromosomes appear. " Meine eigenen Untersuchungen lassen 

 es mir ausgeschlossen erscheinen, dass im Ei der Seeigel Nu- 

 cleolen und Centrosomen irgend etwas mit einander zu thun 

 haben. . . . Dagegen ergeben sich unzweifelhafte Beziehungen 

 der Nucleoli zur Entwicklung der Chromosomen. . . . Dieses 

 Wechselverhaltniss ist nun nicht so zu verstehen, als ware das 

 gesammte Material der Chromosomen in den Nucleoli enthalten. 

 Dagegen spricht die geringe Masse der Nucleolar-Substanz und 

 ihr verschiedenes Verhalten den iiblichen Chromatin-Farbungs- 

 mitteln gegeniiber. . . . Die Nucleolen konnen somit den 

 Chromosomen ein zur endgultigen Fertigstellung nothwendiges 



