52 



THE EGGS OF MAMMALS 



result of pituitary hormone action and the subsequent atresia 

 of the ova containing them occurs because these ova are not 

 Uberated and fertihzed. " Pseudomaturation " spindles have 

 not been reported in hypophysectomized animals although 

 atresia has. 



It has long been the contention of certain observers of 

 ovarian atresia that the apparent parthenogenetic develop- 



t^ 'Mm: 



'»!. 





Fig. 19. Atretic ovum from type 3 follicle in the rabbit. 

 Note fragmentation of cytoplasm and chromatin. 



ment of ova destined never to be liberated is simply an 

 incident of the process of degeneration and is not in fact 

 true parthenogenesis (Hensen, 1869; Balfour, 1882; Sobotta, 

 1899; Janosik, 1897; Bonnet, 1899; Rubaschkin, 1906; Ath- 

 ias, 1909; Kingery, 1914; Kirkham, 1916; Stockard and 

 Papanicolou, 1917; Addison, 1917; Long and Evans, 1922; 

 Clark, 1923; Engle, 19276; Kampmeier, 1929). These in- 

 vestigators have observed varied types of fragmentation of 



