33O HARRY H. CHARLTON. 



not occur, because cleavage spindles are so short lived that the 

 study of a much greater number of eggs would be necessary 

 before coming to any such conclusion. 



SUMMARY. 



The cytological changes which the unfertilized egg of the 

 mouse undergoes in the Fallopian tube and uterus are closely 

 similar to those which occur in the eggs of atresic follicles in 

 the ovary. 



The processes are considered degenerative and have only a 

 superficial resemblance to parthenogenetic development. 



The breaking down of the second maturation spindle of the 

 unfertilized egg usually results in the formation of several or 

 many nuclei. Rarely a single nucleus is formed, in which case 

 the egg does not fragment rapidly and may pass from the uterus 

 before the degenerative processes are complete. 



The eggs with many nuclei divide into numerous cells, of which 

 some are provided with degenerating nuclei. These are further 

 disintegrated and absorbed by phagocytic cells, which make 

 their way into the egg probably through breaks in the zona. The 

 phagocytes from their appearance are polymorphonuclear leuco- 

 cytes, and they evidently act on the cytoplasm causing a vacu- 

 olization of its outer portions and a later crumbling of its peri- 

 phery; the end being a complete disintegration of the egg and its 

 absorption by the phagocytes. 



LITERATURE. 

 Athias, M. 



'09 Les phenomenes de division de 1'ovule dans les follicles de Graaf en voie 

 d'atresie chez le Lerot (Eliomys quercinus L.). Anat. Anz., Bd. XXXIV. 

 No. i. 

 Bonnet, R. 



'oo Giebt es Wirbeltieren-Parthenogenesis? Ergebn. der Anat. u. Entwickl., 



Bd. 9. 

 Heape, W. 



'05 Ovulation and Degeneration of the Ova in the Rabbit. Proc. R. Soc. 



London, Vol. y6b. 

 Hartman, C. G. 



'16 Studies in the Development of the Opossum Didelphys virginiana. Journ. 



Morph., Vol. 27, No. i. 

 Henneguy, L. F. 



'94 Recherches sur les follicules de Graaf chez les mammiferes et quelques 

 autres Vertebres. Journ. d. anat. et d. Physiol., Ann. XXX., No. i. 



