No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 345 



zum individuellen ZelUeben, nicht zur Fortpflanzung; denn beim 

 Beginn der Mitose verschwinden sie, um nach Beendigung der- 

 selben — im Ruhestadium des Kerns — wieder aufzutreten." 

 He notes that their peripheral position is " Eine Lage, die fiir 

 eine Wirkung auf den Zellleib die denkbar giinstige ist." 



Brauer ('94), Actinosphacriiim : in the cyst of the second order 

 (" Ruhecyste") there is a nuclear reticulum consisting of 

 chromatin granules imbedded in a linin network, and usually 

 numerous nucleoli of irregular form, arranged either in rows or 

 circles. Probably the nucleoli take no part in the formation 

 of the chromosomes, and are equivalent to those of metazoan 

 cells ; they disappear in the prophase of mitosis. 



Bunting ('94) found in the eggs of Hydractinia and Podoco- 

 ryne a single large nucleolus, containing one central vacuole of 

 large size. 



Flemming's ('94) " Referat " includes some of the more 

 recent papers on nucleoli. 



Foot ('94), egg of Allolobophora : during the first maturation 

 division the nucleoli are distributed in the cytoplasm. Each 

 pronucleus contains from one to seven nucleoli : " the nucle- 

 oli persist during the cleavage spindle, but how much later I 

 am unable at present to state." 



Hodge ('94), nerve cells of Rana stimulated by the electric 

 current : amoeboid movements of the nucleolus were noticed ; 

 " it was possible to make out granules in the nucleolus which 

 moved slowly about and in several instances were seen to be 

 extruded into the nucleus"; and in cells which had not been 

 stimulated, but simply fixed in osmic acid and stained with 

 safranin, " the granules were stained brighter red than 

 the body of the nucleolus, and several were found partially 

 extruded." 



Lavdowsky ('94) studied nuclei from the epidermis of the 

 fins of Amphibian larvae, as well as various tissues of plants. 

 The nucleolus consists of : (i)an outer, thick " Pyrenin-Chro- 

 matinschale " ; (2) an enclosed vacuole; and in the latter (3) 

 the " Nucleololus " (" das noch in Entwickelung begriffene 

 Centrosoma"). The animal nucleolus varies from a spherical 

 to an angular or star shape. In the resting nucleus the chro- 



