PARTHENOGENETIC CLEAVAGE OF THE 

 ARMADILLO OVUM. 



H. H. NEWMAN. 

 INTRODUCTION. 



In the year 1909 I began a general study of the ovary of the 

 nine-banded armadillo in search of some explanation of the 

 phenomenon of polyembryony. Among the first of the peculiar 

 features to catch my attention were what appeared to be cleavage 

 stages in certain types of ovarian ova. It was thought that this 

 condition might have some bearing on polyembryony but further 

 study and a review of the literature on kindred topics convinced 

 me that these changes were in no sense to be interpreted as 

 stages in normal development. They must, on the contrary, be 

 interpreted as more or less abnormal and abortive attempts, on 

 the part of ovocytes that have reached maturity but have been 

 denied the normal culmination of their destiny in ovulation and 

 fertilization, to develop embryos in spite of insuperable difficul- 

 ties. I should hesitate to contribute another chapter to the 

 already voluminous literature on the supposed parthenogenesis 

 of mammalian ova during follicular atresia had I not at my 

 command evidence of a very crucial character, which seems to 

 me to demonstrate beyond controversy a certain amount of real 

 parthenogenesis in a mammal. 



The ovaries studied are the same as those that formed the 

 basis of a recent paper on maturation and fertilization in this 

 species (Newman, 1912). Those ovaries, fixed in freshly made 

 Zenker's fluid and stained by Bensley's copper chrome haema- 

 toxylin process, give the clearest pictures. 



RESUME OF THE EVENTS OF MATURATION LEADING UP TO 



PARTHENOGENETIC CLEAVAGE. 



In order that the changes preceding cleavage may be under- 

 stood it will be necessary to review the facts dealing with the 

 maturation process which were described in a recent paper 

 (Newman, 1912). The most striking peculiarities of this process 



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