440 
EDWIN G. CONKLIN 
is probably dissolved, while a finely granular yellow material 
gathers around the maturation spindle, the germ nuclei and the 
segmentation spindle. 
Before maturation the gray substance is small in quantity and 
finely granular, and it is readily separated from the clear sub- 
stance ; after maturation it becomes more abundant, more coarsely 
granular or alveolar, and it is separated with greater difficulty 
from the clear substance. 
The clear material may be sharply separated from the yellow 
and the gray before the maturation division; afterward it is 
separated with greater difficulty, and the amount of it which may 
be separated decreases up to the first cleavage. It is especially 
difficult to separate the clear from the gray in the later stages of 
this period. This may be due to increasing viscosity of the 
egg substances in the later stages. In many cases it is known 
that the egg substance increases in viscosity after maturation, 
probably through the loss of water. Many observers have noted 
the loss of water on the part of the egg immediately following the 
maturation and fertilization. In Fulgur (Conklin 1907) this 
change in the consistency of the ooplasm is most notable, the eggs 
being quite fluid in the early stages and much firmer in the later 
ones. 
2. The changes in the relative weights of the three ooplasmic 
substances is shown by the rapidity with which the centrifuged 
eggs orient at different stages. Until the first maturation the 
centrifuged eggs orient very rapidly, with the yellow pole down 
and the gray pole up. After maturation the stratification of the 
substances becomes less and less distinct and at the same time the 
eggs orient more slowly until at the time of the first cleavage this 
orientation is so slow that it usually escapes detection. The same 
is true of eggs centrifuged after the maturation and before the 
first cleavage; such eggs always orient the more slowly the later 
in this period they are centrifuged. This change in the rats of 
orientation may be due in part to a less distinct separation of the 
-three substances in the latter part of this period, owing to the 
greater viscosity of the egg substances. But that it is due in 
large part to changes in the specific weights of the substances 
