326 HARRY H. CHARLTON. 



closed by a tumor, thus preventing access of the sperm to the 

 eggs on that side. The mouse was killed sixty hours after 

 finding the litter. In the tube on the occluded side, two eggs 

 were found, one in the second maturation spindle stage, and the 

 other showing the breaking down of the spindle. In the other 

 horn fertilization had taken place and the eggs were in the four- 

 cell stage. In the figure it will be noted that the chromatin of 

 the spindle has for the most part gone into the formation of a 

 circular vesicle, in which a number of chromosomes remain 

 practically unaltered. 



A later stage picturing the breaking down of the spindle is 

 that of Fig. 6. Here the lobes are larger and have become 

 separated from the central vesicle. All the chromatin is now 

 found in the walls of the various vesicles, none remaining as 

 chromosomes. 



The loss of the achromatic fibers and the breaking down of 

 the spindle is probably due, as suggested by Kingery ('13), to 

 the degenerative changes appearing quite early in the cytoplasm. 

 This is shown by the fact that the cytoplasm stains more deeply 

 than in normal eggs. Numerous dark staining granules are seen, 

 particularly near the periphery of the egg. These constitute the 

 mitochondrial bodies. 



Kingery ('13) is of the opinion that the spindle fibers of the 

 second maturation spindle break and free the chromosomes, 

 which then migrate into the cytoplasm and form numerous 

 nuclear vesicles. In my material the achromatic fibers disappear 

 early, and from Figs. 5 and 6 it would appear that the vesicles 

 may be formed in situ, and not necessarily from chromosomes 

 which have wandered from the place of the original spindle. 



In Figs. 7, 8 and 9 a different process of spindle disintegration 

 is seen. These three eggs are all from the same mouse and were 

 located close together in the lowest portion of the tube very 

 near the uterus. From Fig. 7, it is evident that while the spindle 

 fibers have disappeared; the chromosomes, although contracted 

 and hugged closely together, still retain the form of a second 

 spindle. Several chromatic fragments have evidently broken 

 off and are seen scattered in the cytoplasm. The succeeding 

 stage may be noted in Fig. 8. The individual chromosomes 



