SO-CALLED PARTHENOGENESIS IN THE WHITE 



MOUSE. 



H. M. KINGERY, 



DEPARTMENT OF HISTOLOGY AND EMBRYOLOGY, 

 CORNELL UNIVERSITY, ITHACA, NEW YORK. 



In atretic follicles of ovaries in a number of different mammals 

 the oocytes go through a process which somewhat resembles 

 maturation. Various stages of mitosis are seen and frequently 

 a first polar body is present. In some cases the oocyte is found 

 divided up in a number of small parts some of which contain 

 nuclei. This process has been described as a beginning of par- 

 thenogenetic cleavage and also as degenerative fragmentation. 

 Bonnet ('oo) gives a review of the work done up to that time and 

 after considering all the evidence decides that the mitotic figures 

 seen in such egg-cells are not those of parthenogenetic cleavage 

 but are rather those of more or less abnormal maturation stages. 

 Newman ('13) reviews briefly the work done since Bonnet's 

 paper and presents the results of his studies on the armadillo in 

 support of the view that "a limited amount of parthenogenetic 

 cleavage occurs but that development proceeds no farther than 

 two or three cell divisions." Van der Stricht ('01), who worked 

 on the bat claims that in that form is found a beginning of true 

 parthenogenesis. Rubaschkin ('07), who studied the guinea-pig, 

 and Athias ('09), for the dormouse, state that the phenomena 

 are to be interpreted as degenerative fragmentation which at the 

 most merely resembles parthenogenesis. 



In material which I have been preparing for a study of oogenesis 

 in the white mouse I found that in the ovaries of young mice 

 approaching sexual maturity there is a very extensive degenera- 

 tion of follicles, most marked between the ages of twenty-five 

 and forty days. As the work on this problem has all apparently 

 been done on the ovaries of fully or young adult mammals, it 

 was thought worth while to use the material in these immature 

 ovaries 1 for a study of this so-called parthenogenesis. 



1 The material used for this work consists of ovaries of white mice varying in 

 age from twenty to ninety days. These ovaries were fixed in Carney's fixer 



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