No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 7)79 



dieselben der Kernsaft wieder zu farben beginnt." He con- 

 cludes that the nucleoli are not immediately taken up into the 

 chromatic thread, but dissolve in the caryolymph ; " auch ist 

 hiermit wohl sicher der Nachweis gegeben, dass sie nicht iden- 

 tisch mit den Mikrosomen sein konnen." The nucleoli arise 

 in the meshes of the chromatin network. Strasburger agrees 

 with Flemming that they represent a substance distinct from 

 the chromatin and nuclear sap, but does not consider it to be 

 a living substance, but rather a reserve stuff. 



Guignard ('85) investigated nuclear division in several species 

 of plants. Lilium, young embryo sac : the nucleus usually 

 contains a single nucleolus, which is very large, finely granular 

 in structure, and situated excentrically between the strands of 

 the chromatin network ; with the double stain, methylen green 

 and fuchsine, it stains red, while the chromatin stains green. 

 At the time of the longitudinal division of the chromatin 

 filament, the nucleolus commences to stain less intensely, 

 vacuoles arise in it, and it finally fragments into small pieces 

 which subsequently disappear ; the fine granules appearing in 

 the nuclear sap at this time are not derivatives of the nucleolus, 

 but originate from the cytoplasm when the nuclear membrane 

 vanishes. '• Dans le Liliinn . . . rien ne fournit la preuve d'un 

 apport direct eff ectue dans la formation du f useau par le nucleole, 

 dont la substance se dissout dans le sue nucleolaire, pour 

 s'incorporer et se melanger, . . . aux autres elements figures 

 qui contiennent la chromatine." In each daughter-nucleolus 

 there are several nucleoli of unequal size ; these disappear also 

 in the subsequent mitosis. Clematis, embryo sac: the nucleoli 

 in karyokinesis gradually decrease in size, and it seems " comme 

 si la plus grande partie de leur substance etait absorbee par les 

 segments [chromatiques]." Northoscordnm : here there are 

 several large nucleoli which disappear when the spindle is 

 produced, their substance being possibly incorporated in the 

 chromosomes. In the metaphasic spirem they reappear in 

 contact with the chromatin : "leur aspect g^n^ral fait supposer 

 qu'ils naissent la ou on les aper^oit dans les jeunes noyaux . . . 

 il est a croire que les nucleoles tirent une partie de leur 

 substance, tout ou moins, du filament nucl^aire auparavant 



