No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
533 
nucleolus. Bohm described (’88) the vacuole of the germinal 
spot of Petromyzon as connected by a fine duct with the sur¬ 
face of the nucleolus. Lukjanow (’88) found in the stomach 
cells of the salamander that the nucleolus is apposed to the 
nuclear membrane, through which it discharges an excretion. 
Compare also Van Bambeke (’97a) and Michel (’96). These 
observations would show that the nucleolus in some cases con¬ 
tains a contractile vacuole, and that the fluid substance of the 
latter is periodically discharged from it (cf. Hodge ’94, Van 
Bambeke, ’97, and Michel, ’96). • 
Flemming (’82) considers the nucleoli to be nuclear organs, 
and regards them either as containers or reserve supplies of 
chromatin, or as “ eine chemische Modification, Vorstufe oder 
Doppelverbindung ” of the latter substance; this view is also 
held by Van Bambeke (’85). Zacharias (’85) also thinks that 
they are organs, but does not agree with Flemming that they 
are reserve masses of chromatin; Gjurasin (’93) corroborates 
the views of Zacharias. Strasburger originally contended (’84) 
that they represent reserve material, a view shared by many 
later observers ; more recently (’88) he shows that the nucleolar 
substance may play some part in the formation of the cell 
membrane, but considers that they may also have some other, 
as yet unknown, function. Korschelt (’89) concludes that they 
are formed as depositions of nutritive substances, and that their 
substance “in und vielleicht ausserhalb des Kernes zur Ver- 
wendung gebracht werden sollte.” Rhumbler (’93) assumes 
that the nucleoli (“ Binnenkorper ”) of the Protozoa represent 
“ Reservestoffe ” deposited in the nucleus and consumed in 
the growth of the latter, standing in some connection with the 
chromatin ; they are not organs, but secretions of the nucleus. 
Hacker (’95) concludes that they are not nuclear organs, but 
secretions of the nucleus formed in or from the chromatin 
elements and destined to be discharged from the nucleus dur¬ 
ing mitosis; he observes that the nucleolar substance “ein 
Stoffwechselsprodukt darstellt, dessen Erzeugung in einem 
gewissen Abhangigkeitsverhaltniss zur Intensitat der vegeta- 
tiven Leistungen von Kern und Zelie steht,” and that its amount 
stands in a direct ratio “ zur Intensitat der Wechselbeziehungen 
