210 BULLETIN OF THE 



tween these extremes are to be met with. Nor does it appear that 

 the direction of the spiral is constant, for, while my earlier observations 

 chanced on cases in which the course was left-handed, later studies 

 taught that the reverse was not uncommon, though probably of less 

 frequent occurrence. Thus far I have not seen this spiral arrangement 

 in the rays of the deeper star of the first archiamphiaster. On the other 

 hand, the spiral rays of the outer star, already seen in the case of the 

 first archiamphiaster, are often found in the second. No instance has 

 come under my observation in which this arrangement was traceable in 

 both stars of a given amphiaster.* 



After the formation of the second polar globule, the influence which in- 

 duces the stellate figure seems to quickly wane ; for the rays become less 

 and less extensive, and finally altogether undiscoverable, — a fact which 

 may in some degree explain the differences of extent which prevail in the 

 stellar figures of eggs otherwise presenting apparently the same stages of 

 development. 



The gradual disappearance of the deeper stellate figure is synchronous 

 with other processes most intimately associated with the fate of the in- 

 ner half of the second maturation spindle. Just as in the formation of 

 the first polar globule, so here one half of the equatorial zone of fibre 

 thickenings passes into the globule ; the other half remains in the yolk, 

 and moves along in the direction of the spindle fibres toward the centre 

 of the deeper stellate figure. This centre, however, it does not reach in 

 the condition of a group of thickenings, nor even soon after this form has 

 given place to a more definitely circumscribed structure. 



There is formed, at the expense of this inner zone, upon the com- 

 pletion of the second polar globule, a vesicular structure of irregularly 

 spherical or ovoid form, which is at first homogeneous, or contains at 

 most only a few highly refractive spherical bodies of unequal size. It 

 is asserted that this structure is formed at the expense of the lateral 

 zone of thickenings, not because a direct metamorphosis in the living 

 egg has been observed, but rather as an inference from the fact that it 

 occupies the place of the latter near the centre of the stellate figure 

 when the zone as such has disappeared. Just what the relation of the 

 individual thickenings to the ovoid vesicle is, I am not able to say. 

 Either each becomes a centre about which is grouped a fresh accumula- 

 tion of substance that ultimately unites with neighboring like masses 

 to form the homogeneous contents of the vesicle, whose enclosed corpus- 

 cles (nucleoli) would then be identical with the spindle thickenings, or 



* See p. 535. 



