No. 2.] THE OOGENESIS OF BUFO LENTIGINOSUS. 397 
granules from which new nucleoli develop to undergo the 
same series of changes as their predecessors. When the germ- 
inal vesicle disintegrates at the beginning of the maturation 
period certain of the nucleoli escape dissolution to form the_ 
twelve chromosomes which undergo a double longitudinal 
division in preparation for the maturation mitoses. At certain 
periods during the development of the ova, therefore, the 
nucleus contains no chromatin except that found in the nucle- 
oli, and there is no “individuality” of the chromosomes or any 
reduction in the Weismannian sense during the maturation 
divisions. For Carnoy and Lebrun (16) the most important 
structures in the nucleus are the nucleoli. “Les nucléoles sont 
le chef-d’ceuvre du noyau: ils représent le degré le plus élevé 
de organisation nucléinienne.”’ In another paper (15) the 
statement is made that “les nucléoles sont des noyaux en mini- 
ature. Il renferme toujours un appareil nucléinien filamenteux 
plongé dans un plasma et logé dans une coque mince.” 
Carnoy and Lebrun give a large number of figures which 
are supposed to furnish evidence in support of their conclu- 
sions. They have, however, seemingly overlooked the impor- 
tant stages which give the clue to the nature of the “primitive 
nucleoli’ and of their relation to the chromosomes (Figs. 28- 
39). In many of their figures they show feathery chromo- 
somes similar to those shown in my Figs. 39-41, etc.; yet they 
consider that these chromosomes are products of the resolu- 
tion of the nucleoli, as are also the granular threads which 
correspond to my oxychromatin filaments. The feathery chro- 
mosomes are often figured in pairs, the sister threads lying par- 
allel or intertwined in various ways. Carnoy and Lebrun state 
that these paired filaments are not formed by a longitudinal 
or by a transverse division of a pre-existent nuclear element, 
but that they are either produced by a single filament folding 
back on itself and the parts separating, or they are two fila- 
ments which have been resolved from two nucleoli lying close 
together. Sections of nuclei are given by Carnoy and Lebrun 
which contain numerous nucleoli and no chromatin threads. 
Such figures are considered to prove conclusively that there 
