308 KING. [Vou. XIX. 
has been no continuation of the primitive filament. It is not 
difficult to find sections of the nuclei of the young ova of Bufo, 
particularly at the stages of Figs. 40-44, in which no chromo- 
somes can be found. Such sections are possible because the 
chromosomes, which stain very faintly, are sometimes col- 
lected together at one side of the nucleus and sections passing 
through the centre of the nucleus show only granular karyo- 
plasm, nucleoli, and possibly some of the oxychromatin threads. 
After the yolk has formed, many fixing fluids do not seem to 
penetrate the egg sufficiently well to preserve the delicate struc- 
ture of the chromosomes. I have examined, under an oil im- 
mersion lens, every section of the nucleus of an egg preserved 
in Gilson’s or Flemming’s solution without finding the slight- 
est trace of chromosomes; while in the nuclei of eggs from the 
same ovary that were fixed with chromic acetic or corrosive 
acetic the feathery chromosomes show very distinctly with 
a comparatively low magnification. I have never found a 
nucleus in which it was impossible to find the chromosomes, 
provided the egg had been properly preserved and stained. 
In his earlier work on Axolotl, Fick (28) states that the 
nucleoli are independent structures which probably represent 
“eine Art Reservestoffbehalter.” In a later paper on the ripen- 
ing of the egg of Rana (29) he confirms the work of Carnoy 
and Lebrun and states that during the growth period of the 
oocyte there are several generations of nucleoli which alternate 
with chromatin figures, consequently the continuity of the 
chromosomes is not maintained during this time. Fick con- 
siders that the nucleoli in the egg of Rana represent “‘eine 
Ruheform des Nucleins im Gegensatz zu den Chromatin- 
Figuren und Chromosomen, Formen in denen das Nuclein 
offenbar eine active Rolle spielt.’’ Carnoy, Lebrun, Fick, and 
also Bataillon agree, therefore, with the conclusion reached 
many years ago by Schultze (83) from his study of the ripen- 
ing of the egg of Rana, that the chromosomes “nicht aus 
einem praformirten Kerngeriist entsteht, sondern sich direkt 
aus den winzigen Keimkorperchen herausbildet.”’ 
The observations of other investigators of amphibian 
