THE SOUTHERN SEA LION 143 



breeding season. There is no clearly marked anoestrous period, but immediately after 

 the breeding season there may be a time of more or less complete azoospermy, depending 

 probably on the recent history of the individual. During the winter spermatogenesis is 

 greatly reduced but not suspended, and on the approach of the breeding season (about 

 September) this condition changes rather suddenly to one of full testicular activity. The 

 winter aspect is associated with the occurrence of " teratocytes " in the testes. 



The general behaviour of the animals is in keeping with the histological picture. After 

 the breeding season the bulls spend a great deal of their time in sleep and are frequently 

 seen in very poor condition indeed ; as time passes their physical condition improves and 

 by July bulls may often be seen to take an interest in cows. As the breeding season 

 approaches, a state of rut becomes more and more obvious. 



It is known that the size of the harem varies greatly and it is very probable that some 

 bulls never acquire even one cow. In this event the breeding season would be the less 

 exhausting, and there might well be produced a condition such as that of no. 431 in 

 which there was a subsidence but not a complete cessation of spermatogenesis after the 

 end of the breeding season. 



OESTRUS, IN THE FEMALE 



Ovary. It has been pointed out by Corner (1919) that the actual size of a follicle or of 

 a corpus luteum has not a great significance. There must nevertheless be a minimum size 

 related to sexual activity. Signs of oestrus are present in the uteri of nos. 465 and 457, 

 where the largest follicles are only 07 and 0-69 cm. in diameter, and coitus was observed 

 in no. 483 which had a follicle of 071 cm. The largest follicle is that of no. 521—2-29 cm. 

 — and follicles between 1 and 2 cm. are common. After oestrus there is a marked 

 reduction in size, the follicles ranging from 0-69 down to 0-27 cm. 07 cm. may, therefore, 

 be considered as the minimum size for the active follicle. 



Two newly ruptured follicles were found (nos. 412 and 527) in association with 

 uterine epithelium of 30 and 35 /x ; the ovarian capsules were filled with fluid and the 

 follicles themselves were still in a collapsed state. 



In the formation of the corpus luteum the granulosa cells, accompanied by a consider- 

 able number of leucocytes, advance from the circumference of the follicle from different 

 points, and eventually the whole space is filled, there being no central cavity in the 

 corpus luteum of this species. The fully formed corpus has the appearance of a number 

 of roughly wedge-shaped masses converging on a more or less central point and sepa- 

 rated by fibrous tissue derived from the theca externa, which carries the blood vessels 

 into the substance of the corpus. When the space is filled the cells increase in size and 

 become fully luteinized, producing finally a corpus luteum of normal structure. 



Among the large cells may be found others, smaller and more darkly staining, which 

 may correspond to the theca lutein cells of Corner (1919) which have also been termed 

 paralutein cells (Gatenby, 1924): Corner considers that they are derived from the theca 

 interna. After it has ceased to be functional the corpus becomes fibrous and regresses 

 to what is sometimes called a corpus albicans, and it finally disappears altogether. It is 



