6O H. H. NEWMAN. 



begins to break down, giving appearances like those shown in Figs. 

 7 and 8, which are two sections through the same egg. Another 

 example of the same condition is shown in Figs. 9 and 10, also 

 taken from one egg. In Fig. 7 can be seen one cell with a 

 fragmenting nucleus, a degenerating nucleus in another cell, 

 and an incomplete mitotic figure with only a few small chromo- 

 somes. In Fig. 8 occur three cells all of which show abnormal, 

 though unmistakable, mitotic figures. Such an egg might be 

 considered as a six-cell stage, with a prospect of reaching a ten- 

 cell condition. There is every evidence, however, of approaching 

 death and disintegration in such cases and one would not be 

 inclined to look for much further developmental progress in such 

 unpromising material. In the egg shown in Figs. 9 and 10 there 

 are several imperfect spindles and two small but healthy nuclei. 

 One might be somewhat more optimistic about the ultimate fate 

 of cases of this sort, but, since these cases show about the maxi- 

 mum of development in the present material, such optimism is 

 scarcely warranted. 



Fig. II is introduced especially to show an unusually fine 

 mitotic figure in one of several cells in an egg in which three 

 other cells show more or less normal nuclei. This egg occurred 

 in a follicle in a very advanced stage of atresia and it is rather 

 surprising to find so pronounced a spark of life in a structure so 

 nearly dead. 



In all of the cases cited and in nearly all in which similar 

 phenomena were observed the zona pelucida was dense and 

 quite intact, hence there can have been no invasions of stroma 

 or follicular cells. So all nuclei found must be products of the 

 division of the original germinal vesicle. In more advanced 

 atresia, however, the zona begins to open up cracks which admit 

 hordes of stroma cells and leucocytes that feed upon the dis- 

 integrating egg material and form cell masses that have been 

 interpreted by some authors as the products of embryonic 

 development. In such cases the observer might be inclined to 

 interpret such synthetic structures, which frequently have an 

 epithelial structure, as tissues, equivalent to those formed in 

 normal embryonic development. Leo Loeb ('n and '12) in 

 recent papers interprets as placental tissues certain structures 



