CRITICISMS AND CONCLUSIONS. 47 



Also (p. 75): 



A large number of eggs in different ovaries have been examined, and in every 

 instance where the size of the egg, its slightly denser protoplasm, and the large folli- 

 cle gave evidence of ripeness, the egg was found to be accompanied by the first polar 

 body. This agrees with the observations of Bellonci (1885), and with Sobotta's 

 idea regarding 10 per cent of the eggs, which he believed formed two polar bodies. 



These two statements appear at first sight either to relate to differ- 

 ent stages of maturation or else to be difficult to reconcile with each 

 other; but further consideration leads us to think that the same condi- 

 tions are intended in both. According to the first quotation, a part of 

 the more advanced eggs are only just beginning maturation (spireme 

 or first spindle), while others are further along, showing the first polar 

 cell and second spindle. In the second quotation only the older eggs, 

 those with the first polar body, are mentioned; but it is perhaps fair to 

 infer that here, too (as announced in the first statement quoted), others 

 were just beginning the process of maturation, though it is explicitly 

 stated that "in every instance" the first polar body was present. How- 

 ever that may be, it is clearly stated that in every mouse examined 

 during the height of the breeding season the ovary contained some eggs 

 which showed the first polar cell and the second spindle. Since the author 

 certainly studied and figured (his figs. 12-17) e SS s from the Fallopian 

 tube, it is impossible to avoid the inference that in all females, even in 

 those in which one set of eggs is in the oviduct, the ovaries contain eggs 

 with the first polar cell and the second spindle already formed; that is 

 to say, maturation may begin several weeks before parturition or ovu- 

 lation. But such a state of affairs is incomprehensible to us, because, 

 according to our studies, mice killed during pregnancy and at intervals 

 of 7 and 14 days after parturition furnished ovarian eggs (these have 

 not been included in the 1,000 eggs recorded in table 2) some of which 

 were in fairly large follicles. Those in the largest follicles (eggs which 

 presumably were destined to leave the ovary at the next ovulation) 

 possessed in all cases the germinative vesicle. Such was also the case in 

 mice killed during a period extending from 1 to 13 hours after partu- 

 rition. Eggs with the germinative vesicle, which, as has already been 

 explained (p. 16), do not acquire the first spindle before about 13 hours 

 post partum, manifestly could not originate by the transformation of 

 eggs already possessing a polar cell and second spindle. Moreover, 

 mice which showed a group of eggs in each oviduct never exhibited any 

 of the large follicles in the ovary. Lastly, as has already been demon- 

 strated (p. 15), only two mice furnished eggs in stages as widely separated 

 as those of the germinative vesicle and of the first polar cell and second 

 spindle; and in these two cases the eggs exhibiting the early stage were 

 in one ovary, while the eggs showing the later stage were in the oviduct 

 of the other side of the body. At first the only explanation of the differ- 

 ences between Dr. Kirkham's results and our own which seemed to us 

 possible was that his mice were of a different breed from ours. 



