CHANGES IN THE OVARY 151 



The changes undergone by the discharged follicle have also 

 been studied in certain of the lower Vertebrates. Giacomini,' 

 who has investigated the subject in birds, amphibians, and, 

 more particularly, Elasmobranch fishes, describes an hyper- 

 trophy of the follicular epithehum consequent upon ovulation. 

 The discharged folHcle of Myliobatis is described and figured as 

 a glandular body in which the enlarged epithelium is pene- 

 trated by an extensive ingrowth of connective tissue and blood- 

 vessels. Wallace ^ gives a somewhat similar account of the 

 spent folKcles in the fishes Zoarces and Spinax. In the latter 

 especially there is a pronounced hypertrophic enlargement of 

 the foUicle cells, associated with thecal ingrowths arrayed in 

 a radial manner. Lucien ^ has described corpora lutea in the 

 reptiles Anguis and Seps, in which there is a simple hypertrophy 

 of the folhcular epithehum unaccompanied by mitotic division. 

 Similar structures in reptiles have also been observed by 

 Mingazzini,* who beheves them to be identical with mammaUan 

 corpora lutea. On the other hand Biihler,* who investigated 

 the ovaries of Cyclostomes and certain Teleosteans, was 

 unable to find any hypertrophy of the wall of the spent follicle, 

 and Cunningham,* also writing on Teleosteans, arrived at the 

 same result as Biihler. However, it is evident that the epithehal 

 theory of the origin of the corpus luteum receives confirmation 

 from those members of the lower Vertebrata in which there is a 

 follicular enlargement following ovulation. 



The mammahan corpus luteum may contain a central clot 

 composed of blood derived from the vessels of the folhcular wall 

 which gave way at the time of ovulation. In this case the 

 blood-clot becomes gradually absorbed along with the remainder 



' Giaoomini, " Contributo all 'Istologia dell' Ovario del Selaci," Mcerca 

 Lab. di Atiat. Normale delta Roy. Univ. di Jionia, vol. v., 1896. 



'' Wallace (W.), "Observations on Ovarian Ova, &c.," Quar. Jour. Micr. 

 Science, vol. xlvii., 1903. 



' Luoien, "Note pr61iminaire sur les premieres Phases de la Formation 

 des Corps Jaune chez certains Eeptiles," C. R. de Soc. de Biol., vol. Iv., 1903. 



* Mingazzini, " Corpi Lutei verie falsi da Rettili," Ricerca Lab. di Anat. 

 Normale della Roy. Univ. di Roma, vol. iii., 1893. 



' Biihler, "KUckbildung der Eif ollikel bei Wirbelthieren," Morph. Jalir., 

 vol. XXX., 1902. 



° Cnnningham (J. T.), " On the Histology of the Ovary and of the Ovarian 

 Ova in certain Marine Fishes," Quar. Jour. Micr. Science, vol. xl,, 1897, 



