24 



Dli. SLUXIN'S THKORIES. 



Ml'. Lucas further uotes: "From tlie examination of a large series (200) of ovaries 

 it can safely be said that there is nothing whatever to corroborate Ur. Slunin's state- 

 ment that it is possiljle to determine from the api)earance of the ovaries how many 

 young a cow has borne. The surface of the ovary does not bear scars corre8i)ouding 

 in number to that of the pups, for not more tban two sears, and this very exce])tion- 

 ally (o cases in 200), are present ou an ovary at one time. The scar of imi)regnation, 

 corpus luteum, develops ver^' slowly and slowly disappears, a cross section of the 

 ovary revealing its preseure long after all traces have disappeared from the surface. 

 Dr. .Sluuin, it is stated, examined the ovaries in alcohol, and he probably mistook 

 the slight dejn-essions caused by the shrinkage of the Graafian Ibllicles for scars. 

 A section of the uon functional ovary shows it to be a fine-grained, homogeneous 

 mass with no developing fo'licle, while the ovary which is for the seiison functional 

 may have as many as eight Graafian follicles in various stages of development. 

 There has not yefc lieeu time to earcifully examine the ovaries bearing two scars, but it 

 may safely be set down as a general rule that the first ovum to reach maturity is 

 fecundated, so that to repeat the statement made above, ovulation and impregnation 

 are practically synonymous." 



COPULATION. 



There is no reason to think that the serving of cows in the ordinary harem causes 

 any serious drain on the vitality of the bull. A bull has been observed by Mr. True 

 to copulate twice within half an hour. The season during wliiih his services may 

 be retjuired extends over a period of fully sixty tlays. 



In copulation the male assumes the position usual in dogs and related animals. 

 The feuKile lies iirone u](on the ground and t)ears his <-lumsy weiiiht. It is not likely 

 that copulation takes ]dace elsewhere than on the islands, and ne\'er at sea except 

 occasionally on rocks awash off the shore. Here young bulls sometimes secure young 

 females in heat, and impregnate them without leaving the water. It is possible that 

 copulation begun on a rock might continue even after the rising water floated the 

 animals off. A case of this kind is recoided by Mr. Tiue, but none was seen by us. 

 As the virgins do not appear on the rookeries before the last of .July, there is not 

 much doubt that the first ]>eriod of gestation is somewhat shorter than thi' others, 

 those coming in heat early in August liearing i)U]is early in .Inly. 8uch a difference 

 is found in horses. I am indebted to Mr. Frank \V. Covey, of Palo Alto, for statistics 

 showing that with ten virgin mares the period of gestation varies from 328 to 344 

 days, the average being 336.8; with ten adult mares, the range is 332 to 360, the 

 average 347.8. 



The first pup noticed on St. Paul the present season was seen ou Keef Rookery 

 June 14. It was then apparently several days old. The last birth witnessed was on 

 Zapadni Rookery August 14. No record of early instances of copulation was made. 

 The first case witnessed by us was on North Rookery of St. George July 9. The last 

 instance of copulation seen was on Tolstoi Rookery, St. Paul, August 27. 



BKLATED IMPREGNATION. 



It is evident, also, from the actions of the old bulls, a certain percentage of whom 

 return in September to their places ou the breeding grounds after feeding, that 

 should any cow fail to be served in .June, July, or August she would tind st^rvice even 

 in September, fhat such belated service sometimes occurs is borne out by the fact 

 that seseral hundred small black pu])s were noted in October ou the rookeries of St, 

 Paul. One of these, killed on October 18, was found in good condition and with 

 stomach full of milk. It weighed Hi pounds. .\n unl>orn f(etus, taken from a cow 

 ou Zapadni Reef August 14, weighed 11 pounds, and the experimental pu]), taken 

 from Zapadni rookery on August 1, supposed to be about a mouth old, weighed 12 

 pounds, A gray ])ui), killeil at the same time as the small black one, weighed 

 29 pounds, and two weeks before a similar pup had been killed ou the same rookery 

 which weighed 33:^ pounds. The little pup could not have been much over a month 

 old, and therefore must have been born in September, 



HEIGHT OF THE SEASON. 



The height of the season, or the period when the most pups are born and sex activity 

 is greatest, is from July 6 to July 15. At this time the harems are held in rigid con- 

 trol by the bulls, who are constantly "rounding up'' their cows and crowding them 

 close together. At this time, however, only about half the adult cows and none of 

 the 2-year-old8 have arrived. When these have come, most of the earlier cows have 

 gone away to feed. At no time, therefore, are much more than half the cows present 

 on any given rookery, and the count of any individual harem can be only an approxi- 

 mation. 



