276 ^rONTGO^IERY. [Vol. XV. 



Eimer ('73), nervous system of Beroe: each nucleus contains 

 one large nucleolus. " Aufmerksamer Beobachtung kann es 

 nicht entgehen, dass jede Epithelzelle von einer Primitiv- 

 fibrille versorgt wird. . . . Ich kann nur so viel sagen, dass 

 ich dieselbe [Primitivfibrille] stets auf das Centrum des Kerns 

 zugerichtet sah, so dass ich zu der Ansicht hinneige, es werde 

 sich spaterhin ihre Endigung im Kernkorperchen feststellen 

 lassen." 



Fol ('73) noticed in the egg of Geryonia fungiforniis one 

 large nucleolus, containing one large, or several smaller 

 vacuoles. 



Auerbach ('74). This important paper I have been unable 

 to consult in the original, and quote from citations by 

 R. Hertwig ('76) and Flemming ('82). According to Auerbach 

 the nucleus is originally a vacuole in the protoplasm, around 

 which a layer of the latter becomes differentiated to form a 

 nuclear membrane. In this vacuole a nucleolus appears 

 later, being derived from the protoplasm, either by a separa- 

 tion of particles from the nuclear membrane or is produced 

 out of those protoplasmic particles which had penetrated 

 from the protoplasm into the original vacuole. He distin- 

 guishes " enucleolar," " uninucleolar," and " multinucleolar " 

 nuclei, the first being the more primitive state. The nucleo- 

 lus has the value of an elementary organism : as long as it 

 is homogeneous, it is comparable to a cytode ; when a vacu- 

 ole appears in it, the latter stands in the same relation to 

 the nucleolus as this does to the nucleus, so that that vacuole 

 may be considered the nucleus ("Kern") of the nucleolus. 

 The original single nucleolus can divide into numerous nucle- 

 oli, and the latter, by the disappearance of the nuclear 

 membrane, become free, and each develops into a separate 

 cell. Auerbach considers this theory as "eine vorlaufige, 

 noch mit Vorbehalt aufzustellende und welter zu prijfende." 



A. Brandt ('74) observed in life (in the blood fluid) slow 

 amoeboid motions of the single nucleolus of the egg of Blatta. 



Flemming ('74) investigated the egg of Anodonta. In young 

 eggs the nucleolus consists of two apposed spheres of equal 

 diameter; in larger eggs one of these spheres is much larger 



