90 FOLLICULAR DERIVATIVES IN VERTEBRATES III 



formations, the oolemma remnants inside them subsisting for 

 a long time. 



The processes so far described lead to the formation of a 

 perfect corpus luteum. Through the transformation of the 

 granulosa cells into lutein-cells and their contact with blood- 

 vessels the active area of the corpus luteum is noticeably 

 enlarged: this implies that the former ovular content can be 

 transformed into hormone within a short time, and rapidly 

 secreted into the blood. 



The /?-phase has the following characteristics:— 

 (i) assimilation of the ovular substances already taken into 



the cytoplasm by the granulosa cells; 

 (ii) movement of the nucleus towards the centre of the cell; 

 (iii) rapid multiplication of the cells; 

 (iv) movement into the ovular space; 

 (v) formation of oviductin in the granulosa cells; 

 (vi) presence of numerous bloodvessels in the ovular space. 



c. The y-stage. As soon as the corpus luteum has matured, 

 it begins to disintegrate. Substances still present in the cells 

 are transformed into oviductin. The vacuoles become smaller 

 owing to loss of hormone, and the lutein cells are reduced in 

 size. Eventually the wall of the follicle collapses, and both 

 blood- and lymphvessels gradually disappear. The cytoplasm 

 of the lutein cells grows denser as the vacuoles are lost. The 

 cell content of the theca becomes looser. With this the actual 

 stage of decay has set in. 



One of the chief characteristics of this stage is the formation 

 of an intensely orange-coloured pigment, inside the lutein 

 cells (Figs. 67 and 68), a property to which the corpus 

 luteum owes its name, a similar pigment being present in the 

 corpora lutea of mammals. As far as our cytological know- 

 ledge of the matter goes, the formation of the yellow pigment 

 would seem to be the result of degeneration of the granulosa 

 cell cytoplasm; for the entire plasmatic cellular content falls, 

 apart into yellowish red granules, which retain their peculiar 

 colour even after the cell has been stained. At this stage only 

 little of the former distinction between granulosa and theca 

 can be seen. All the cells eventually fuse to form a spherical 



