[1897 Embryology. 731 
trospheres swell and a swelling is conspicuous at the equator of the 
spindle (where reagents show the equatorial plate dividing) while the 
astral rays become very long aad curved, convex towards the egg sur- 
face. 
The egg protoplasm now begins to move actively again in streams 
that set the spindle into slow pendulum-like movements. This stream- 
ing takes place alternately in each end of the egg and consists of move- 
ments from the pole toward the equator. 
The cleavage plane appears suddenly as a groove on the surface of 
the egg at one side, and the internal streaming of protoplasm coming 
down from the pole towards this equatorial groove turns inwards and 
then back towards the pole. The same takes place on the opposite side 
of the egg, and the cleavage plane instantly cuts across through the 
e 
Amongst unusual cases the author mentions the interesting fact that 
the movement of the protoplasm may temporarily bend the first cleay- 
age spindle so much that its “ fibres ” become wave-like, while these 
same movements may make‘the astral rays twist into spirals, as seen 
by Mark in Limax. External pressure exerted on the eggs may bring 
about the same bending of spindle and rays. The author concludes 
that all the egg—spindle and astral rays included—is always plastic and 
liquid, though the material of the spindle of the rays is more viscid 
than the rest. 
After the first division the larger of the two cells soon shows proto- 
plasmic streamings again, and curious ridge-like pseudopodia rise up 
from its surface near the edge of the cleavage plane. Blunt pseudo- 
podia may form on other parts of the surface, but the amceboid move- 
ments of the first two blastomeres are not as pronounced as those of the 
fertilized egg. 
In the second division each cell shows streaming movements from the 
poles to the equator, and before the cleavage plane appears the spindle 
is seen to vibrate from side to side. 
When the four cells are forming they glide over one another into a 
new arrangement, and in so doing they are much distorted by pressure— 
even the spindle within them being distorted. 
The paper contains many other interesting facts regarding the cleay- 
age phenomena, both as seen in living and in preserved eggs, but we 
will only note certain facts that speak for the view of Bütschli as to the 
vesicular or foam-like structure of protoplasm. Besides all the above 
facts that show the liquid and viscid state of even the most firm parts 
of the egg—the fibres—the author sees an appearance of vesiculation at 
