23 



take up their positions and await the arrival of the females, which event is accom- 

 pauied by constant lighting among the males. The earliest cows appear the tirst 

 week in ,Iiine. They come on land but a short time before the delivery of their pups. 

 After delivery the females are held in the harems by the bulls until after impregna- 

 tion, when they go to sea to feed, returning at intervals to nurse their young. 



THE cows. 



The cows do not come in all at once. The period of their arrival, and consequently 

 of the birth of pups, extends from early in .June until the middle of August, with, 

 probably scattering births as late as the first week in September. The female lirst 

 comes in heat at the age^f two years. The virgin * two-year-olds come to the islands 

 late, lew, if any, before the last week in .July. They are not found on the rookeries 

 at the height of the season. In the last week of .July and the first week of August 

 they are gathered with late-coming adult cows in harems outside of the rookery 

 proper; most of them J)ehind it. 'Ihese harems are usually in charge of young bulls, 

 and have not the stability of the adult harems, as most of the young cows do not 

 remain after impregnation and their places are taken by others. 



GESTATION. 



The period of gestation is about three hundred and fifty-five days, or a little less 

 than a year. For virgin females it is without doubt somewhat shorter, as none of 

 these are impregnated before the 2.5th of .1 iily. The uterus has two horns or l)ran(he8, 

 one to the right, the other to the leit, and the single pup is l)orn in one of these boms. 

 Soon Jitter parturition, app.'trently witliin a week, the ovary of the op])osite side 

 matures iin ovule, the cow comes in heat, and is covered by the l)ull. The second 

 pup is thus develoi^ed in the other horn of the uterus. While the first horn is recov- 

 ering from gestation antl parturition the second is made ready for gestation. For 

 the rest of tlif life of the animal a pup is borne each jear on alternating sides. 



The development of the fietus is at first very slow, as it remains minute during 

 the whole period of lactation. Nothing is known of its growth in the winter. At 

 the time ol' birth in June or .July the pup is large and far a<lvaiiced in development 

 as compared with the young of most mammals. Its weight at l)irth is from !) to 12 

 pounds, and it is very soon al)le to find its way about the rookeries. We can only 

 conjecture as to the age attained l»y fur seals — possil)ly 10 to 1.5 years for females and 

 15 to 20 for males, but this is a guess only. There is no reason to lielieve that either 

 males or females outlive the power of procreation. The oldest female recorded, 

 judging age by the wear of the teeth, was in milk when speared. There is no doubt 

 thait all female fur seals Jtreed annually, and no reason to think that any cow in heat 

 escapes impregnation. Mr. Lucas finds on examination of the ovaries of many cows 

 killed at sea that in each case examined impregnation has taken place on first com- 

 ing in heat. To this there are probal)ly very few exceptions. These would appear 

 the next year as late-boni pups of adult mothers. 



SCAllS ON THE OVARY. 



Whether a cow is impregnated or not, can be determined by the scar in the ovary. 

 As to this we quote th<' following from notes of Mr. Lucns: 



"As it may naturally be asked, What reason is there for supposing the scar on the 

 ovary to be the scar of impregnation and not merely the rupture of a (Jraafian follicle? 

 it may be answered that — 



"Of the 190 ovaries examined by Mr. Townsend, Mr. Barrett-Hamilton, and myself, 

 in only one case did an ovarjMjear more than a single scar, and in this case the second 

 scar was faint. 



"In specimens obtained early in September the ovarian scar and the corres])ouding 

 branch of the uterus had increased in size, showing clearly that impregnation had 

 taken place, and it is not assuming too much to say that in the fur seal ovulation is 

 practically synonymous with impregnation. That this should be so is not surprising 

 when the facts in the case are considered. 



"In the first place, a female after entering into a harem is held there until the bull 

 is satisfied he may properly allow her to leave, while back of the harem and in the 

 water in front are idle bulls watching for stray females. 



"Finally, when the harem system is relaxed there is an influx of young Inills, who 

 before this time could not enter the rookeries, and if every female were not impreg- 

 nated they would be likely to discover the fact."' 



* The categories of fur seals here called virgin two-year-olds and virgin yeaTlings 

 were shown to be such by the killing and dissection of individuals, the two-year-olds 

 from the small harems behind the Reef rookery, the yearlings from the bachelor 

 herd of Lnkanin ; still others were lassoed for examination and released. 



