GERM CELLS IN NEMATODES, SAGITTA 183 
3. Tae Keimpann IN OTHER MetaAzoa 
Certain phenomena have been reported in the 
early development of the eggs of many other animals 
which have either been compared or can be compared 
with conditions such as we have described in the 
preceding portions of this book. 
The large nucleolus in the germinal vesicle of the 
medusa, Avquorea forskalea (Fig. 55, A), according 
to Haecker (1892), disappears from the germinal 
vesicle about half an hour after the egg is laid, and 
a similar body becomes evident near the egg nucleus 
which has in the meantime become smaller (Fig. 55, 
B). These two bodies are considered by Haecker 
to be identical, and the term “Metanucleolus” has 
been applied to them. The metanucleolus is, in each 
division up to the sixty-four cell stage, segregated 
intact in one cell. Its further history was not 
traced, but in the blastula (Fig. 55, D) when the cells 
at the posterior pole begin to differentiate, nucleolar- 
like bodies appear in some of them which are absent 
from the undifferentiated blastula elements. These 
may be the descendants of the metanucleolus. 
A body similar to the metanucleolus was also dis- 
covered by Haecker near the copulating germ nuclei 
in the egg of Aurelia aurita, but its history could not 
be determined because of the large amount of yolk 
present. Haecker identifies the metanucleolus of 
Aiquorea with the spherical body described by Metch- 
nikoff (1886) near the egg nucleus of Mutrocoma 
anne, and considered by him as a sperm nucleus. 
