No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 525 



I have found a wandering of nucleolar substance out of rest- 

 ing nuclei in one very beautiful and unique case, namely, in the 

 subcuticular gland cells of Piscicola ; at one stage in its cycle 

 of development the nucleus commences to contract in volume, 

 and in so doing discharges all except a single one of its nucleoli 

 into the cytoplasm. This and certain of the observations cited 

 from other investigators show that a discharge of nucleolar 

 substance from the resting nucleus takes place in some cells. 

 But the more recent observations of Morgan, Floderus, and 

 others on Tunicate development render it very probable that 

 Fol and Roule were mistaken in assuming that the nucleoli 

 which pass out of the germinal vesicle become the constituents 

 of follicle cells. There is still some question, also, as to whether 

 the nucleolar substance in the cytoplasm takes any part in the 

 formation of the yolk substance. Other pertinent observations : 

 Mertens ('93), Bremer ('95a, b), Kosinski ('87, '93), Galeotti ('95), 

 Melissinos and Nicolaides ('90), Auerbach ('74), Ver Ecke 

 ('93), Steinhaus ('88), Rohde ('96). 



1 1 . Behavior of Nucleoli during Nuclear Division. 



It is in cases of nuclear division that the nucleolus has 

 received the most attention from morphologists. The behav- 

 ior of the nucleolus in mitosis and amitosis may be treated 

 separately. 



I . Amitosis. — In this mode of nuclear division it is frequently 

 the case for the nucleolus to divide first, so that each of the 

 daughter-nuclei receives a half, or approximately a half (for the 

 division of the nucleolus is not always into two equal parts), 

 of the parent-nucleolus. In support of this deduction the fol- 

 lowing observations may be mentioned : Schaudinn ('94, A7noeba 

 crystalligera); F. E. Shulze ('75, A. polypodia); Will ('85, ova of 

 Nepa, Notonecta) ; Doflein ('96, degenerating ova of Tubularia); 

 Carnoy ("85, ova of Gryllotalpa, Lithobius, Geotrupcs) ; Korschelt 

 ('95, intestinal cells of OphiyotrocJia) ; my observations on the 

 peritoneal cells of Polydora ; Hoyer ('90, intestinal epithe- 

 lium of Rhabdonema) ; Frenzel ('93b, hepatopancreas cells of 

 AstacHs) ; Plainer ('89a, Malpighian tubes of Dytiscns ; Wheeler 



