680 
J. P. Munson 
reticulum of the surrounding cytoplasm. If this felted mass were entirclv 
expanded, it would resemble the rest of the cytoplasm, in all respects, 
except that a system of radial fibers would doubtless become visible as 
in fig. 32. In this case the central body is stained bright red witli acid 
fuchsin, wliile the surrounding granules are blue from the hematoxylin 
stain. As there is never more than one body like this in each egg, I cannot 
consider it anything but a centrosome, attraction sphere and aster. The 
astral rays are distinctly visible throughout most of the cytoplasm. In 
fact one gets the impression that the cytoplasm is a liuge aster. Compare 
figs. 26 a and 33 with figs. 39 and 40. 
That this body lias the structure of an aster as distinct as that in 
any fertilized egg, may be seen by comparing fig. 37 from the oocyte of 
Limulus, with fig. 68 from a fertilized egg of Ascaris. 
If this typical centrosome and aster in the ovarian egg originates 
de novo from amorphous granulös, scattered throughout the cytoplasm, 
and often said to originate from nuclear cliromatin, it slioidd be possible 
to find more than one of these in an egg. But that is never the case. 
Such Strange forms as that seen in figs. 45, 47, 49 and in figs. 65, 66, 
and in fig. 36, are probably due to unequal distribution of yolk granules, 
causing condensation of fibers, whicli present different appearances 
according to the plane in whicli it is sectioned. The typical aster like that 
of fig. 73 where no distortion has been produced by yolk granules or meta- 
plasm, seems to be a sphere, the same in appearance in wliatever plane 
looked at. 
In the large eggs, when definite yolk bodies make their appearance, 
the sphere and aster are obscured. But its presence is still indicated by 
a large, solid granulär body surrounded by a clearer ring, fig. 28; or eise 
by a large ring of deeply staming yolk granules occupying the center of 
the cytoplasm, and having a relation to the germmal vesicle, fig. 48, 
similar to that seen in the youngest oocytes, fig. 25. Something similar 
can be seen in the large eggs of the tortoise. 
As the yolk accumulates in and around the center, the germinal ve- 
sicle is crowded nearer to the periphery of the egg, between whicli and the 
germinal vesicle a clear spongy protoplasm appears, fig. 48. The latter 
finally spreads out over the surface of the egg, as the germinal vesicle 
approaches the surface. This point is the animal pole ; wliile the center 
determines the vegetative pole, as in the spiders and the tortoise. 
There is in this egg, too, a distinct polarity, which must be attributed 
to definite structural elements persisting throughout the growing period of 
the ovarian egg. I liave elsewhere shown (65) that this polarity does not 
