248 WILLIAM B. KIRKHAM. 



The remaining three virgin mice were killed March 30, 1909, 

 and of those born in the preceding December, the Fallopian 

 tubes of one yielded nine eggs, similar to those mentioned above, 

 except that seven still showed first polar bodies; the ovaries of 

 the other animal had upon them the white scars indicative of 

 well formed corpora lutea, and no sign of eggs was found in 

 either Fallopian tube. Both sets of ovaries contained a number 

 of mature eggs undergoing degeneration. The female mouse born 

 in January showed no signs of having ovulated, no evidence of 

 either young or old corpora lutea being found on either ovary, 

 nor any trace of eggs in the Fallopian tubes. The ovaries of 

 this animal, however, have in them several eggs with first polar 

 bodies and second polar spindles, but all appear to be degen- 

 erating. 



From these observations we may safely conclude that not only 

 is ovulation in adult female white mice independent of pairing, 

 as stated by Sobotta ('95 and '07), and by the writer ('07), but 

 that it is an independent process from the start, maturation and 

 ovulation occurring in the females without regard to pairing, 

 although at present we do not know wilji what regularity. 



These results, also, are not only of general interest, but they 

 possess value as showing the mouse to be an eminently suitable 

 mammal upon which to investigate the possibility of artificial 

 parthenogenesis. 



A further fact which should be noted here, is the change of 

 opinion, on the part of the writer, regarding the fate of the first 

 polar body formed by the mouse egg. In 1907 the writer stated 

 that his observations led him to believe that when the first polar 

 body was not found with the egg, it had been forced through the 

 zona pellucida at the time of ovulation. That same year Lams 

 and Doorme ('07) published a paper on the development of the 

 mouse egg in which they stated that the first polar body in that 

 animal underwent degenerative changes leading finally to its dis- 

 appearance. These authors figured a few first polar bodies in 

 an advanced state of atrophy, and the present writer has since 

 confirmed their conclusions, using some material of his own ob- 

 tained since the publication of his first statement on the subject. 

 A fairly complete series of degenerating first polar bodies — some 



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