1 1 2 FOLLICULAR DERIVATIVES IN VERTEBRATES III 



y. The significance of the post -ovulation corpus luteum. 

 The sexual-endocrine organization of mammals has hitherto 

 been the centre of interest, and is accordingly most widely 

 kwown. 



We now know that, probably through a pituitary factor 

 acting on the theca, the latter secretes, in the follicular stage, 

 the estrogen which causes the uterus to hypertrophy and 

 prepares it for pregnancy (the so-called proliferation stage) 

 (Fig. 76C). After ovulation, the granulosa luteinises under 

 the influence of a second pituitary factor, and produces 

 progesterone, which brings the uterus, primed by estrone, 

 into the secretion-phase, thus rendering pregnancy possible. 

 The post-ovulation corpus luteum persists and continues to 

 function for a long time during pregnancy. 



Cooperation with the corpora atretica should be viewed in 

 this way, that it guards the adnexa against involution, both 

 before puberty and during the interestrus, so that with the 

 appearance of the first corpus luteum a normal response may 

 be assured again (Fig. 76B). This applies chiefly to mam- 

 mals. In birds and reptiles, however, post- and pre-ovulation 

 corpora lutea appear both simultaneously and in succession, 

 (and frequently in equal numbers). From the frequency 

 with which the pre-ovulation corpora lutea occur in the 

 interestrus and in youth we may draw the conclusion that 

 here, too, they play their part in the preparation of the ovi- 

 duct, for shell-formation in oviparous reptiles and birds, 

 whereas the post-ovulation corpus luteum in viviparous rep- 

 tiles flourishes for a longer period when it serves for the 

 nourishment of the developing ovum. In oviparous Saurop- 

 sidans the post-ovulation corpus luteum is only present for 

 a brief period; gland formation is incomplete, and its function 

 in providing the ovum with its shell probably of minor 

 significance (Fig. 76C). 



d. The significance of the calyx. Ovulation leaves a scar 

 in the ovary wall. It is the task of the calyx to repair this 

 defect. The calyx is typical of Anamnia, and is always found 

 in conjunction with the pre-ovulation corpus luteum (Fig. 

 76C) , which appears already long before ovulation, keeps the 



