220 BULLETIN: MUSEUM OF COMPARATIVE ZOÖLOGY. 
siderably enlarged. The male pronucleus has also increased in size and 
followed the lead of its attraction sphere toward the centre of the egg. 
In the dorsal half of the section is seen the female pronucleus, already 
grown to considerable size. ln it can be discerned small chromatic 
granules, and behiud it and deeper in the section the female archoplasm. 
This archoplasm seems to be much less energetic than that of the male 
element, for its influence is scarcely perceptible, even on the portion of 
the egg in which it lies, and it does not appear to modify either the shape 
or course of the female pronucleus, which, as we shall see, moves toward 
the male archoplasm leaving its own behind. The polar globules repre- 
sented at the margin of this section do not as a matter of fact occur in 
that position, but at the margin of the preceding section. If that sec- 
tion were properly superposed on this, the polar globules would lie over, 
but a little to the left of the female pronucleus. 
A stage semewhat later than the one just described, though found in 
the same lot of eggs, is shown in Plate 11. Figures 7-10, which represent 
the fourth, seventh, tenth, and twelfth sections respectively of a series 
of sixteen. In Figure 7 is seen the male pronucleus with its archoplasm 
now divided ; in Figure 8, the female pronucleus ; in Figure 9, the female 
archoplasm ; and in Figure 10, the polar globules marking both the 
centre of the future dorsal surface of the embryo, and the point from 
which the female pronucleus starts in its journey through the egg toward 
the male pronucleus. "The position of these various bodies with relation 
to one another can be most clearly illustrated by two reconstructions 
(Figs. 11 and 12) upon planes perpendicular to the plane of sectioning 
and at right angles to each other. Suppose the sections piled one above 
another in their original order and position, the first section of the series 
being uppermost and the egg thus reconstructed to be viewed as a trans- 
parent object in the direction of the arrow at the left of Figure 7. One 
would then see the appearance shown in Figure 11, which is a projection 
of the egg and the most important bodies in it upon a plane parallel to 
the line ab (Fig. 7), and perpendicular to the plane of Figure (6 
If the egg be viewed in the direction of the arrow at the top of 
Figure 7, one gets the appearance shown in Figure 12, which is a pro- 
jection upon a plane parallel with the line a’ Y in Figure 7, and perpen- 
dicular to the plane of that figure. 
A comparison of the stage under discussion with that represented in 
Figure 5 shows that considerable changes have occurred in the interval 
between them. The male pronucleus (Fig. 7) has grown to much 
greater size and contains several conspicuous chromatic granules. In- 
