Some Problems of Reproduction: a Comparative Study of ...

SOME PROBLEMS OF REPRODUCTION. 51
vesicular nucleus, the germinal vesicle, with its chromatic
elements concentrated and fused into a spheroidal mass, the
germinal spot, supported by a delicate network of " intranuclear
protoplasm," "nucleo-hyaloplasm," or "linin." In
the structure of its nucleus the ovum recalls the only other
cells that enjoy a prolonged life uninterrupted by fission, and
that attain to an equally large size—somatic ganglion-cells.
The first symptom that marks the maturity of the ovariau
ovum and its return to active life is the disappearance of its
nuclear wall, and the merging of part of its " achromatin"
contents, together with the true nucleoli, in the cytoplasm;
while the chromatic elements of the germinal spot become
separate as rods. It is to this process and stage that we must
refer the elimination of mere trophic elements from the
nucleus of the ovum—a process in many ways comparable to
the disorganisation of the meganucleus of the conjugating
Ciliates. There is every reason to believe that the nucleus of
a cell destined to lie quietly feeding and fattening for days,
months, years, or decades, must be of a very different character
from one that has to undergo rapidly repeated fission; in
other words, between a purely anabolic and an essentially
katabolic nucleus. If we accepted Greddes and Thomson's
view, 1 that there are actually entities that we can term
anastates and katastates, we should have to reject their conclusions,
and say that this preliminary disorganisation of the
germinal vesicle is the elimination of its anastates : for henceforward
all the phenomena manifested are katabolic, even
without the advent of the male; and in ova which are not
parthenogenetic the resumption of anaboly is henceforward
impossible. This process is to some extent comparable
with the elimination of the trophic element of the spermatogonium,
the blastophore, nucleated or non-nucleated j
but the parallel is a very remote one, and purely physiological.
1 A view which I no more accept than I do Sachs's view, that roots are
formed at the base of a wallflower and flowers at the top by the migration
downwards of "root-forming," and upwards of "flower-forming substances"
(Wiirzel und Blumen-bildende Stoffe).