THE LEOPARD SEAL 261 



SEXUAL MATURITY 



Males. Pieces of testis and epididymis from the following have been sectioned: 

 nos. 651, 653, 654, 655, 657, 662, 664, 665 and 666. Of these nos. 651 and 653 are the 

 two smallest animals and the sections are obviously those of juvenile testes: the lumina 

 of the tubules are not yet developed, and there is of course no trace of spermatogenesis. 

 In no. 657 the organ is somewhat more advanced, since lumina are beginning to appear 

 in the form of irregular central spaces in the tubules, but spermatogenesis has not 

 begun. Of the remaining six, three, nos. 654, 664 and 665, are in a state of almost 

 complete inactivity: a few sperms only may be found by searching and large syncytial 

 cells are present in all, although fewest in no. 664 which is the least active. No. 654 

 has a very few sperms in the epididymis and no. 664 none. The last three testes are 

 those of nos. 655, 662 and 666; no. 662 shows a slight amount of general spermato- 

 genesis, and a mass of sperms which is of limited size appears in three or four contiguous 

 sections of the epididymial tubule. The other sections of it in the same slide are empty. 

 Nos. 655 and 666 are both more active than no. 662, but neither of them appears to be 

 fully so. Sperms are present in the ducts of both and there are syncytia in the testis 

 of no. 666. 



From the evidence available, derived from the condition of the os penis and the testes, 

 it must be concluded that sexual activity does not begin until the third year, and that 

 animals of that age are adolescent, the fourth year being that of sexual maturity. There 

 does not appear to be a definite anoestrous season in the male of Hydrurga as a species, 

 but this does not exclude the possibility of a resting period for individuals such as 

 no. 665. 



Females. Ovaries of six non-pregnant animals have been examined. The two first- 

 year animals, nos. 661 and 663, have characteristically juvenile organs, although under 

 the microscope a very early stage of a Graafian follicle was found in the ovary of no. 

 663. In the second-year seals, no. 656 has many primordial follicles and numerous 

 developing Graafian follicles of microscopic size. This animal was killed in October 

 and was a virgin. S.S. i, killed 18 January, has folhcles up to 4-5 mm. in diameter and 

 a corpus luteum of 26 mm. longest diameter, and B. 144, killed 12 February, has 

 numerous follicles up to 7 mm. and two corpora lutea, one recent and one older. 

 Ovaries of the third year are all of pregnant animals and are three in number, but the 

 one non-pregnant ovary, B. 142, from a mature seal (fourth year or over) was collected 

 on 27 January and shows fairly numerous follicles with a maximum of 6-5 mm. and 

 four corpora lutea of different ages, the largest being 30 by 18-5 mm. It is a matter for 

 regret that the evidence is not more conclusive, but I do not consider that one may 

 safely go further than to state that it seems highly probable that this species may begin 

 ovulating in its second year, but does not always do so, and that it commonly becomes 

 pregnant in its third year, perhaps for the first time. The third year therefore should 

 be considered as the year of sexual maturity at present. 



