No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
541 
zum Vorschein, und zwar in unregelmassigen, oft betrachtlichen 
Entfernungen von einander.” When the nuclei wander towards 
one another the nucleoli move about, “ indem sie innerhalb 
des Kernraums allerlei gerade, zickzackformige, bogenformige, 
Bahnen durchlaufen, mit einer vergleichsweise erheblichen 
Geschwindigkeit, so dass zuweilen in weniger als einer Minute 
Strecken von der Lange des Kern-Durchmessers zuriickgelegt 
werden ”; during these movements the nucleoli remain perfectly 
spherical. When the copulation nuclei are apposed the nucleoli 
in them suddenly disappear, and the mode of this disappearance 
was determined in one case, though it is exceedingly rapid ; “ das 
Kiigelchen wurde allmahlich blasser und etwas grosser und fuhr 
dann plotzlich auseinander, ein Wolkchen bildend, welches einen 
Augenblick darauf nicht mehr zu sehen war.” The nucleoli 
reappear in the resting nuclei, and in the successive genera¬ 
tions up to the eight-cell stage have the same cycle of changes, 
except that in each generation they are somewhat larger than 
in the preceding. These nucleoli are formed independently of 
one another. By the re-formation of the nuclear vacuole a 
number of cytoplasmic granules pass into the cavity of the 
nucleus, and there fuse to form the nucleoli. 
Reinhard (’ 82 , cited by Braem, ’97) describes in the egg of 
Plumatella different stages of the nucleoli, which may be single, 
double, or even trilobular. 
Wistar Institute of Anatomy and Biology, 
Philadelphia, February 3, 1897. 
