THE SOUTHERN SEA LION 145 



virgin are few and undeveloped, being little more than strings of cells. In the sections 

 the amount of glandular tissue visible is relatively small during oestrus, the lumina are 

 large and the amount of secretion small or there may be none. Mitoses are present in 

 the epithelium, appearing there later than in the corresponding cells of the uterus. After 

 ovulation the amount of glandular tissue visible increases greatly and it may occupy 

 the greater part of the stroma ; the lumina of the glands decrease in size owing to the 

 growth of the epithelial cells from a more or less cubical to a columnar form, and secre- 

 tion becomes plentiful. This condition declines towards the end of the post-ovulation 

 phase but traces of it are sometimes found in the early part of oestrus, from which it 

 may be concluded that one cycle may follow another fairly rapidly. It is not clear whether 

 the increase of glandular tissue is due to proliferation of already existing glands or to an 

 increase in their actual number. 



As has been stated by Deansley and Parkes (1933) placental blood vessels may survive 

 for a considerable time in an occluded form so that in section they appear as hyaline 

 discs with few nuclei. In Otaria this condition has frequently been observed in seals 

 of which it was known that they were post partum and also in others in which there was 

 no gross appearance to suggest it. 



In some of the uteri, particularly those of animals of the largest size, it was observed 

 that there was what might be termed an accumulation of these vessels to such an extent 

 that the stroma of both cornua was largely occupied by this tissue. The hyalinized blood 

 vessels present impassable barriers to the growing glands and uteri which contain such 

 vessels in large proportions are incapable of full glandular development. A similar 

 phenomenon is observable in the post-partum cornua of seals which have ovulated after 

 parturition and are in a state of pseudopregnancy or tubal pregnancy. It is difficult to 

 avoid the conclusion that the uteri which display the hyalinized vessels in great abund- 

 ance and are not recently post partum have passed the height of their breeding activity 

 and are in this manner showing signs of senility due to the loss of those powers of 

 recuperation which are necessarily correlated with continued sexual activity. 



Oestrus may, and probably always does, occur almost immediately after parturition. 

 Thus seal no. 53 1 , which had given birth so recently that the uterus was still uncon- 

 tracted, had the epithelium of the sterile cornu elevated to 17/x and oestrous changes 

 were in progress. I consider that this animal could not possibly have been more than 

 twenty-four hours post partum. 



Sperms were found in uteri with an epithelial height which varied from 20 (no. 477) 

 to 53 p (no. 414) and related to follicles from 071 cm. upwards. No. 477 has, therefore, 

 been taken as marking the beginning of oestrus as differentiated from pro-oestrus, and 

 an inspection of Table VIII will show that the transition from the follicular phase 

 (oestrus) to the luteal (pregnancy or pseudopregnancy) is marked by the disappearance 

 of mitoses from the uterine epithelium and the onset of great glandular activity: the 

 height of the epithelium decreases steadily during the luteal period. 



Coitus has already been described (1934)' but il ma y be added that ' judging by what 

 was found in the uteri of newly served cows, the amount of semen emitted is surprisingly 



