MUSEUM OF COMPARATIVE ZOOLOGY. 203 



distributed, show about the animal pole irregularities of arrangement, 

 which at first sight give one the impression that the outline of the outer 

 stellate sphere is not even. This is most noticeable when the view is 

 upon the animal pole, as in Fig. 24. However, the archiamphiaster, seen 

 in profile, shows — whichever way the vitellus is rotated about the spin- 

 dle axis — that this appearance is produced by aggregations of granules 

 quite outside the stellate sphere, and that really the surface of the latter 

 is not invaded by these granulations. 



Inasmuch as the stage just described has not been seen by other 

 observers, it will not appeaf superfluous to state briefly the evidence that 

 it is the second archiamphiaster. The stages with which this might most 

 easily be confounded are without doubt that of the formation of the first 

 archiamphiaster, and that of the first cleavage amphiaster. 



1. The Qgg in question was one of four of nearly the same degree of 

 advancement (Figs. 25, 22, 23, 57). Three of these were subjected to 

 acid at intervals of ten minutes, the first (Fig. 25) being immersed on 

 the appearance of a conical protuberance ; the second (Fig. 22), though 

 ten minutes later, seems to have been hardly more advanced than the 

 first. This one (Fig. 23), the third, was observed to have a conical ele- 

 vation ten minutes before its immersion, although the elevation may 

 possibly have first appeared a few minutes earlier. It must have been 

 then at the least ten minutes after its appearance, and most likely 

 more, perhaps even fifteen or twenty minutes, when the conditions here 

 preserved became fixed. This in itself would be enough to preclude the 

 possibility of the first mistake, even if the first polar globule were no 

 longer to be discovered in contact with the vitellus. There can be no 

 doubt, then, that the first polar globule had already been formed, and 

 that consequently the figure in question could not be the^rs^ archi- 

 amphiaster. 



2. The second possibility may not at first appear so easy of refuta- 

 tion. The position of the axis of the spindle relative to the already 

 formed polar globule, it is true, is little in harmony with the inter- 

 pretation of the figure as the amphiaster of the first cleavage sphere, 

 and is exactly what we might expect of a second maturation spindle. 

 Nevertheless, it might be urged that possibly the polar globule is no 

 longer located at that point of the vitelline surface where it originated, 

 and that consequently the relation of the spindle axis to the globule is 

 quite valueless in determining the nature of the spindle ; for in that case 

 the polar globule here figured might be the second, and the stellate figures 

 accordingly could only be interpreted as belonging to the first cleavage 



