present, are not depicted in IV., V., VI., and
VII.

VIII. Equatorial arrangement of the four chromatin loops in the
middle of the now segmenting ovum: the achromatic substance forming
a spindle-shaped system of granules with fibres radiating from the
poles of the spindle (attraction-spheres); the chromatin forms an
equatorial plate. (Compare Fig. 36 G.)

IX. Shows diagrammatically the commencing separation of the
chromatin fibres of the conjugated nuclei, and the system of fibres
radiating from the attraction-spheres. (Compare again Fig. 36 G.)
_p.c._, polar circle; _e.c._, equatorial circle; _c.c._, central
particle.

X. Further separation of the chromatin filaments. Each of the
central particles of the attraction-spheres has divided into two.

XI. The chromatin fibres are becoming developed into the skeins of
the two daughter-nuclei. These are still united by fibres of
achromatin. The general protoplasm of the ovum is becoming divided.

XII. The two daughter-nuclei exhibit a chromatin network. Each of
the attraction-spheres has divided into two, which are joined by
fibres of achromatin, and connected with the periphery of the cell
in the same way as in the original or parent sphere, III.]

As I shall have more to say about these processes in the next volume,
when we shall see the important part which they bear in Weismann's
theory of heredity, it is with a double purpose that I here introduce
these yet further illustrations of them upon a somewhat larger scale.
The present purpose is merely that of showing, more clearly than
hitherto, the great complexity of these processes on the one hand, and,
on the other, the general similarity which they display in egg-cells and
in tissue-cells. But as in relation to this purpose the illustrations
speak for themselves, I may now pass on at once to the history of
embryonic development, which follows fertilization of the ovum.

* * * * *

We have seen that when the new nucleus of the fertilized ovum (which is
formed by a coalescence of the male pronucleus with the female) has
completed its karyokinetic processes, it is divided into two equal
parts; that these are disposed at opposite poles of the ovum; and that
the whole contents of the ovum are thereupon likewise divided into two
equal parts, with the result that there are now two nucleated cells
within the sph