472 WESLEY R, COE, 



Fig. 4. The asters have increased greatly in size, and the centro- 

 somes are surrounded with a very conspicuous centrosphere. The 

 nuclear membrane has been pushed in, and dissolved away in the 

 vicinity of the asters. The chromatic network is becoming much less 

 conspicuous. The stain remains in the yolk- globules, so that the cyto- 

 plasmic reticulum is not apparent. 



Fig. 5. A similar stage in which the centrospheres are very 

 conspicuous. 



Fig. 6. The two asters were more widely separated than in the 

 two preceding figures, and their fibres have made their way through 

 the body of the germinal vesicle , leaving its walls intact above and 

 below. The chromosomes lie mostly in the upper portion. The yolk- 

 globules retain their stain only near the periphery of the egg. 



Fig. 7. The asters have drawn nearer together , and their fibres 

 are uniting to form a spindle. The nuclear membrane has disappeared 

 entirely. The chromosomes are drawn up near the asters, and are seen 

 to be in direct contact with the aster-fibres. The centrosomes at each 

 pole of the spindle have already divided. Reconstructed. 



Fig. 8. A slightly later stage in which the chromosomes are being 

 drawn into the equator of the spindle. Only one of the two centro- 

 somes in each aster is shown. The centrospheres are less evident than 

 at an earlier stage. X ^^0. 



Fig. 9. The first polar spindle is fully formed. It has greatly 

 contracted while moving to its definite position at the periphery of the 

 cell. Only one of the two centrosomes in its outer pole is shown. The 

 spindle is imbedded in the deeply staining protoplasm which was 

 derived from the germinal vesicle. 



Fig. 10. The second polar spindle has formed, and is rotating to 

 its definite position. The spermatozoon is seen on the left. Its centro- 

 some, but not its aster, has divided. 



Fig. 11. The sperm-centrosomes have separated with the formation 

 of a distinct central spindle. The aster, the halves of which are 

 separating with the formation of a central spindle, has left the spermato- 

 zoon far behind to the right. 



Fig. 12. Both polar bodies have formed. The radiations remaining 

 in the egg from the second polar spindle are grouped about the chromo- 

 somal vesicles which are uniting to form the egg-nucleus. The 

 sperm-nucleus, with its two large asters in close proximity, is moving 

 towards the center of the egg. Reconstructed. 



Fig. 13. Six nucleoli in successive stages of dissolution. The 

 two upper, left-hand figures show an inner homogeneous body, staining 

 like chromatin. The next three show a vacuole of increasing size, while 

 of the last only a cup-shaped portion remains. X ^^O« 



Fig. 14. A young sperm-aster which shows its relation to the 

 cytoplasmic reticulum, and to the yolk-globules. Surrounding the centro- 

 sphere is a broad area of protoplasmic substance entirely free from 

 yolk — all the yolk - globules having been pushed peripherally. 

 X 1500. 



