46 THE FUR SEALS OF THE PRIBILOF ISLANDS. 



The young females come on the rookeries for the first time after the harems of 

 adults have broken up, and there is more or less admixture of seals of all ages. They 

 are not in the harems in June or early in July, and in 1896 they were first seen on 

 St. Paul July 27, and on St. George July 28, their appearance on the two islands 

 being thus practically simultaneous. As to the age of these cows and the fact that 

 this was their first appearance on the rookeries there can be no question ; the yearlings 

 and 2-year-olds are readily known by their size, while to settle the point beyond 

 dispute, two young cows were shot and examined on July 28, both proving to be 

 2-year-old virgin females. From the last of July until about the end of August these 

 2-year-old cows were numerous. 



The congested condition of the. blood vessels and the presence in both ovaries of 

 Graafian follicles in various stages of development show that in young females coming 

 to the rookery for the first time both branches of the uterus are functional, and 

 impregnation may ocpur in either. The young are borne alternately on either side, 

 and if, for example, the first pup is developed in the right branch of the uterus, the 

 second will be borne in the left, first one ovary then the other being functional. The 

 reason for this alternation is that the time between delivery and coming in heat is so 

 short that therei is not sufflcient time for that branch of the uterus in which the young 

 was developed to resume its normal condition, this operation probably requiring six 

 weeks. All this was very well demonstrated by Mr. Townseud in his report for 1895, 

 and his statements have been corroborated in every particular. The difference in 

 size between the ovaries, and particularly between the branches of the uterus, is 

 usually perceptible, not only to the eye, but to the touch, until late in August or 

 early in September, although by that time specimens will be met with in which the 

 impregnated branch has commenced to swell while the other has nearly or quite 

 resumed its normal size. After the maturing and impregnation of an ovum the other 

 Graafian follicles appear to be absorbed, since in ovaries examined in September 

 where the corpus luteum was well advanced the Graafian follicles were small. 



There is not the slightest evidence to support the theory advanced by Dr. Slunin 

 that the seal breeds.biennially, for all evidence tends to show that from the third year 

 onward throughout life the female brings forth a pup annually. 



It is commonly stated that the females come in heat within 48 hours and that the 

 period of gestation is about 360 days, but more accurate information is needed on 

 these points, and I am inclined to doubt the correctness of the above statements, 

 or at least am unwilling to accept them as a general law. From data obtained in 

 1897, given in full at the end of this chapter, it would seem that from three to six 

 days elapse between the birth of the pup and the coming in heat of the cow. In 

 1895, the season being late, Mr. Townseud made the following observations on the 

 condition of the harems June 25 and 26 : "The harems in course of formation along 

 the beaches were as yet very small, the average number of females in each being 

 five. About one-fourth of the females were nursing new-born pups, the others being 

 conspicuously gravid. Some sections of rocky ground were still covered with snow, 

 and a number of new-born young with the red placentae still attached were lying upon 

 the snow. Occasional females were noticed arriving from the sea, but none w-ere seen 

 leaving. There were no signs of any then coming into heat." If the interval between 

 delivery and coming in heat is so short as generally supposed, it would seem that some 

 of these females should have evinced some signs of desire. Moreover, if the period of 



