355 



of serial sections cut about 10 (W thick and stained with Haematoxyliu 

 and Eosin. Constant reference has been made to the slides of corpora 

 lutea of pregnant animals for the purpose of comparison and these 

 slides have also been re-examined in order to verify certain points. 

 The following ovaries were employed: 



Ova not shed. 

 Series 1. Animal getting into heat. 



„ 2. Animal more advanced in heat. 

 „ 3. Ovaries nearly ripe. 

 ,, 4. Ovaries ripe. 

 „ 5. Ovaries ripe. 



Ova shed. 



Series 6. Six days after Copulation. Ova may or may not be 

 fertilized. 



„ 7. Seven days after Copulation. Ova not fertilized. 



„ 8. Few days after heat. No Copulation for 21 days. 



„ 9. Some time after heat. No Copulation for 37 days. 



„ 10. Probably one day after Copulation. 



„ 11. Five days or more after heat. No Copulation for 5 days. 



,, 12. Twelve days or more after heat. No Copulation for 12 days. 



„ 13. No record of heat or Copulation. 



„ 14. No record of heat or Copulation. 



„ 15. Sixteen days after Copulation. 



„ 16. Twenty days after frequent copulation. 



„ 17. Eighteen days after Copulation. 



„ 18. No record of heat or Copulation. 



„ 19. No record of heat or Copulation. 



In the above list, the ovaries from 6 — 19 are arranged approxi- 

 mately according to the state of development of their corpora lutea 

 and may be roughly divided into three groups, Nos. 6 — 9 the period 

 of formation, Nos. 10 — 14 the period of growth, and Nos. 15—19 a 

 period of maximum size. 



The primordial follicle, its transformation into a Graafian follicle 

 and the ripening of the latter have already been dealt with by 

 Sandes (18) and his description leaves nothing to be added. Sandes' 

 paper indicates that the life of the corpus luteum may be dealt with 

 conveniently in three stages, 1) Period of formation, 2) Period of 



23* 



