No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
395 
concludes that the nucleolar substance, dissolved in the nuclear 
sap, may be used in the production of the spindle fibers. 
Koernicke (’96), study of mitosis on Triticum: in the devel¬ 
opment of the embryo sac when the two pole nuclei fuse 
together, the two nucleoli also join to form one. In the mitosis 
of the pollen the nucleolus always disappears before the forma¬ 
tion of the spindle, but it could not be determined whether it 
takes any part in the formation of the latter. 
Lauterborn (’96), nuclei of diatoms: there are several nucleoli 
present; in the spirem stage of division they commence to 
gradually disappear ; “ es scheint mir ziemlich sicher, dass ihre 
Substanz mit derjenigen der Chromatinkornchen und des 
Liningeriistes zur Bildung der Knauelfaden verbraucht wird.” 
It is important to note that the central spindle arises outside 
of the nucleus, before the nucleoli begin to disappear, so that 
there can be no genetic connection between the two. 
Poirault and Raciborski (’96), binucleated (“conjugate”) 
Uredineae during the production of the ascidiospore generation : 
in the mitosis the nucleolus becomes extruded into the cyto¬ 
plasm, almost always in the equatorial plane. “ Bei manchen 
Arten bleiben sie sehr lange erhalten so z. B. bei Peridermium 
Pini acicola , wo neben den langst ruhenden, mit neuen Nukleo- 
len versehenen Kernen noch in den Plasma, die alten Kern- 
korperchen der Elternkerne herumirren. Mit den Centrosomen 
haben somit diese extranukleolaren, vakuolirten Nukleolen 
nichts zu thun.” 
Zimmermann (’96), a general critical summary upon the 
vegetable nucleolus, with consideration of a part of the previous 
literature. Nucleoli are almost always present in the cells of 
the higher plants, and are of wide occurrence also in the lower 
forms ; double staining serves to differentiate them from the 
chromatin. There are usually from one to three to a nucleus, 
but in the embryo sac of Lilium martagnon there are from 
twenty to thirty. In Chara the older nuclei show the nucleolar 
substance in the form of very numerous, irregular fragments. 
The distinction of “ Hauptnucleolus ” and “ Nebennucleolus ” 
is not tenable, since the latter may be possibly chromatin 
globules. “Mit dem Chromatingeriist scheinen die Nukleolen 
