494 



7) The constriction which results in the formation of the first 

 polar globule is completed in 5 or 10 minutes. It passes midway bet- 

 ween the two lateral zones and is accompanied (always?) with the for- 

 mation of a highly refractive disklike structure (Zellplatte Strasburger) . 



8) The thickenings of the external zone are grouped in a single 

 plane near the centre of the polar globule ; those of the internal zone 

 lie at the surface of the large, homogeneous sphere which occupies 

 the centre of the deeper aster. Both stain deeply in carmine. 



9) In optical cross-sections of the spindle it is seen that the fibre- 

 thickenings of both equatorial and lateral zones are neither distributed 

 evenly over the circular area of the spindle, nor yet in strictly peripheral 

 position. There is, however, an unmistakable grouping of the thickenings 

 near the circumference of the spindle. 



10) The rays of the peripheral aster, modified in their direction, 

 are still to be traced when the polar globule is nearly detached, but 

 ultimately all disappear. 



11) After the formation of the first polar globule the deeper aster 

 recedes from the animal pole, and there arises, in a manner not yet 

 discovered, a second archiamphiaster of two complete spherical asters, 

 one of which (the external) is more sharply defined than the other. 



12) The second polar globule is formed from the external aster 

 and corresponding half of the second maturation spindle in substantially 

 the same manner as the first polar globule, about an hour after the 

 appearance of the first globule. 



13) The polar globules are cells, and their nuclei are formed from 

 the external zone of nuclear fibre- thickenings. 



14) During the formation of the polar globules the internal aster 

 sometimes presents a peculiar and, I believe, hitherto unobserved 

 appearance. The radiate filaments in passing from the internal pole of 

 the maturation spindle to near the surface of the yolk, make a grand 

 spiral sweep. 



15) This spiral arrangement is in some cases very pronounced, 

 many of the rays traversing upward of 400°; in other cases it is only 

 feebly expressed. The spiral may be either dextral or sinistral. The 

 same phenomenon , though less extensive , has also been seen in the 

 polar globule, or external aster. 



16) The rays of the internal aster gradually disappear after the 

 formation of the second polar globule. 



17) The fibre-thickenings which constitute the internal zone in 

 the second maturation spindle unite to form the female pronucleus, 

 which is at first small and homogeneous, but soon enlarges and ex- 

 hibits nucleoli. The female pronucleus is therefore formed in a manner 



