No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 
529 
he finds that in mitosis it changes into chromatin. Rabl (’85, 
larval cells of amphibians) and O. Schultze (’87, ova of Rana 
and Triton) contend that the nucleolar substance takes some 
part in the formation of the nuclear filaments ; but Born (’ 94 ) 
subsequently found that these filaments stand in no connection 
with the nucleolar substance. Holl (’93, ovum of Mus ) finds 
that the central granules of the nucleoli wander out of them 
and so become the chromosomes. Van Beneden (’ 75 , ovum of 
Lepus) originally supposed that the nucleolus becomes the first 
pole body. Kastschenko (’90, ova of Selachii ) finds that all the 
nucleoli disappear in the spirem stage, while Rtickert (’92) 
finds that a few of them pass into the cytoplasm. Stuhlmann 
(’86, ova of Insecta ) finds that the nucleoli gradually disappear 
during the maturation of the egg ; and similar conclusions 
were reached by Stauffacher (’93, Cyclas), Rhumbler (’95, 
Cyphoderia ), Sheldon (’90, Peripatus)> Heathcote (’86, Julus ), 
Van der Stricht (’95, Amphioxus ), Brauer (’92, Branchipus ), and 
Vejdovsky (’82, Sternaspis). Auerbach (’96, spermatogonium 
of Paludina) holds that the nucleolar substance becomes incor¬ 
porated with the chromatin elements. Meunier (’86) and Moll 
(’93) for Spirogyra , and Carnoy (’85) for other cells also, hold 
that the chromosomes are derivatives of the chromatin skein of 
the nucleolus. Heuser (’84, mitoses of various plant cells) con¬ 
tends that the nucleoli become gradually apposed to the nuclear 
filaments, and that their substance unites with these elements, 
though in some cases a superfluous portion of the nucleolar sub¬ 
stance may be discharged from the nucleus. Korschelt (’95, 
ovum of Ophryotrocha) finds that the nucleolus gradually dis¬ 
appears by dissolving in the nuclear sap, and believes that a part 
of this substance may be introduced into the nuclear filaments. 
Zacharias (’85) somewhat prematurely concludes that the nucleoli 
always disappear in mitosis. Tangl (’82) finds that in Hemerocal- 
lis , in uninucleolar nuclei, the nucleolus dissolves in the nucleus, 
but in those which are multinucleolar one may pass out into the 
cytoplasm ; in Hesperus and Cisium they gradually disappear. 
Humphrey (’94, plant cells) holds that “die Nucleolen in einigen 
Fallen aus der Kernhohle, bevor sie von den karyokinetischen 
Kraften angegriffen werden, austreten konnen.” 
