194 BULLETIN OF THE 



according as they would naturally lie near to, or more remote from, the 

 continuation of the spindle axis. The course of some of the fibres of 

 even the deeper half of this star is thus affected. The result is a 

 gradual diminution in the number of fibres in the outer half of the 

 aster, and their greater concentration near the equator of the astral 

 sphere. It is this increase in the number of the fibres near the equa- 

 tor of the aster, together with their arched course, which causes 

 the peculiar funnel-shaped phenomenon already described. Such sim- 

 ple, and yet unique, modifications of the star are not the only ones 

 to be found. While I believe the backward deflection of the fibres 

 is an invariable, a mechanically necessary feature of this stage of the 

 Qgg phenomena, I am not able to say as much of some other modi- 

 fications ; in fact, I am almost certain that the latter are to be found 

 only occasionally. They may not, perhaps, on that account, prove less 

 interesting. I refer to the very peculiar appearance sometimes pre- 

 sented by the outer aster, when one looks directly down upon the animal 

 pole of the egg. Instead of seeing the fibres radiate in straight lines, 

 as one might naturally expect and would find in the majority of cases, 

 it will often be discovered that they are uniformly bent into a spiral, pre- 

 senting thus a figure not unlike that of a turbine water-wheel (Fig. 56). 

 The curvature in the cases I have seen (remembering that the observer 

 is looking upon the animal pole) is such as would be produced by the 

 peripheral ends of the fibres being moved in the direction in which the 

 hands of a clock advance, while the centre remained fixed, or by an 

 opposite rotating motion of the axis of the spindle when the peripheral 

 ends were immovable. 



This spiral phenomenon has been observed even before the aster had 

 caused any elevation of the surface (Fig. 47), but not before it had 

 reached the periphery of the yolk. No phenomena corresponding either 

 to flattening, backward deflection, or spiral arrangement of the fibres, 

 have been observed in the deeper star up to this stage. 



During the stage now under consideration the centre of the peripheral 

 sphere becomes conspicuously modified. It is at length occupied by a 

 circular, highly refractive homogeneous body, flattened in the direction 

 of the axis of the spindle so that it appears oval in a profile view. 

 This body, at times irregular in outline, appears to be surrounded by 

 a clear zone of uniform thickness. The appearance may be due solely 

 to reflection from the body itself (Comp. Flemming, '78^ p. 310.*) 



* The numbers immediately following an author's name serve the double purpose of 

 referring the reader to the list (p. 591) where the titles of papers are given, and of in- 

 forming him at once of the approximate date of the paper in cpiestion. 



