622 
T. H. MORGAN 
ence on the falling egg, and its weight would seem too insignificant 
to act as a load. So far as the evidence goes, it shows that eggs 
fall at random, but the stalk is lost in many eggs, making identi- 
fication difficult. It should, of course, not be overlooked that a 
partial orientation of the egg may be possible. Those eggs that 
have a long distance to fall may orient, while those already at the 
bottom of the tube may become caught by surrounding eggs and 
fail to orient. Only a proportionate count of eggs in relation to the 
location of the polar spindle could settle the question. 
The evidence on the whole is in favor of random falling for the 
egg of Cerebratulus, i.e., the eggs do not orient, at least not to any 
considerable degree. 
There is a consequence of some importance involved in this 
result which shows that the distal spindles are carried central- 
wards. This means that the spindle retains its form although 
carried half way through the egg in consequence of the rearrange- 
ments involved. If the centrosomes be centers of force we must 
suppose that in their passage through the egg as just described the 
asters are in process of reformation and absorption at every step 
of their progress. This is as necessary to the center of force as- 
sumption as it is necessary to assume that particles of iron rear- 
range themselves as the magnetic poles move through them. 
But when we recognize the time element in the building of the 
aster in the normal egg it seems incredible that this interpreta- 
tion can be correct. Possibly the situation might be met by 
the assumption, that, not only the spindle, but its surrounding 
medium, is moved as the yolk fills up the lower hemisphere. 
Opposed to such a view is the fact that the yolk does not com- 
pletely fill its hemisphere, but lies imbedded in the ground ma- 
terial already present there, and this material is sufficient in 
amount to bring about division, showing that it is not incon- 
siderable. Moreover in some eggs the polar spindle passes through 
the yolk to reach the surface, showing that there still remains 
in the yolk field enough of its material to act as a polar field. 
But it may not be so much the amount of material as the molec- 
ular directions of that material that give the axial relations. 
The evidence, while it does not disprove completely the center 
