450 KING. [More cine 
finds large nucleoli which have a very complicated structure, 
being composed of a number of deeply staining balls sur- 
rounded by a mass of granules. 
No matter how many plasmosomes a nucleus may contain 
there is usually one of these bodies that is larger than the 
others (Fig. 29); and one of the first indications of the ap- 
proaching dissolution of the nucleus is the formation of a 
fluid space around this large nucleolus (Fig. 17). The nu- 
cleolus itself at this time may appear homogeneous (Fig. 18), 
or it may contain one or many vacuoles (Fig. 17). In 
either case it stains less intensely than in earlier stages and it 
gradually decreases in size (Figs. 26-27), while the vacuole 
around it constantly grows larger (Figs. 18, 26, 29). As the 
fluid space becomes several times the size of the original 
nucleolus, its substance cannot be derived entirely from the 
nucleolus, but it must be obtained in part from the dissolution 
of the karyoplasm. The vacuole grows until it comes in con- 
tact with the nuclear membrane (Fig. 26). It then breaks at 
some point in its outer surface and the nuclear substance is in 
direct contact with the cytoplasm, as during the growth of 
the vacuole the nuclear membrane becomes very irregular in 
outline and it disappears entirely when the vacuole breaks 
(Fig. 27). While these changes are taking place the chromo- 
somes gradually break up into granules that cannot be dis- 
tinguished from the karyoplasm, and by the time the nuclear 
membrane has disintegrated most of the chromosomes have 
disappeared (Fig. 27). During the disintegration of the nu- 
cleus I have never found the chromatin in the form of ir- 
regular clumps as Ognew has found to be the case in the 
degenerating cells of Bidder’s organ in Bufo vulgaris. The 
degenerative changes just described are not found in the cells 
of Bidder’s organ until the young toad has attained a length 
of about 2 cm. 
Degenerative changes usually appear in the cytoplasm soon 
after the stage of Fig. 19, since only in rare cases is a cell able 
to form yolk spherules. If a cell contains a large number of 
yolk-nuclei at the time that these degenerative processes begin 
the yolk-nuclei are dissolved in situ, leaving clear fluid spaces 
+ 
