i 24 DISCOVERY REPORTS 



MATERIAL AND METHODS 



Since the field work necessitated residence as near as possible to a seal rookery I 

 selected Cape Dolphin on East Falkland, as I was already familiar with it, and erected a 

 standing camp which was supplemented by a turf hut to serve, inter alia, as a laboratory. 



The principal obstacles to progress were the difficulty, at times, of finding seals 

 suitable for killing and the impossibility of working the same grounds daily, since this 

 would have disturbed the animals too much, and, finally, the necessity of carrying 

 everything to and from the camp on pack horses. 



After spending some time watching the winter herd I came to the conclusion that I 

 could discern, by inspection, cows which were not pregnant, owing to their more 

 elegant figures, and experimental killings showed this to be correct, although the matter 

 was complicated by the necessity, from humanitarian reasons, of making every effort 

 not to kill cows which were suckling pups; but such cows usually have mammary 

 glands so well developed that they can be distinguished. 



Seventy-two females were collected, and of them n were pregnant. The remaining 

 6 1 non-pregnant or apparently non-pregnant animals were taken in every month of the 

 year except April and May. When it became obvious that there was a good deal of 

 sexual activity among the cows throughout the year and that it apparently did not 

 always result in pregnancy, in order to ascertain if there were an anoestrous period in 

 the males, a short series of them, 1 1 in all, was killed, nine of them during what may be 

 termed the "off season", that is, outside the easily recognized breeding season: these 

 bulls were, with one exception (no. 415, see p. 140), the largest which could be found. 



The animals were all shot in the brain with a -22 rifle, using the " long rifle " cartridge ; 

 this was in every way satisfactory, since the skull is very little injured and the largest 

 bulls are killed if the bullet is well placed. 



After a seal was shot it was always stabbed in the heart, partly as a precaution and 

 partly to reduce the torrents of blood which otherwise pour over and obscure everything 

 when these animals are opened immediately after death. The total length of the animal 

 was measured in as straight a line as possible from the tip of the snout to the end of the 

 tail. 



With cows the animal was opened in the mid ventral line, the ovaries were excised, 

 split to allow access of the fixative and placed in Bouin's aqueous fluid. Segments of 

 the uterine cornua were also fixed and fragments of vagina, etc. when such specimens 

 were indicated. With the males small pieces and sometimes whole testes were fixed. 

 Notes were made on the fresh tissues as requisite. The entire reproductive systems of 

 four cows were collected ; one was preserved in spirit and the other three in salt, that is 

 to say, they were covered with dry salt and allowed to make their own brine. After 

 many months these specimens were soaked in repeated changes of fresh water to extract 

 the salt and finally brought up through the alcohols to 70 per cent : they have retained a 

 most agreeable flexibility, and have made exceptionally good material for dissection. The 

 skulls were roughly cleaned and dried for transport, and to each was attached a bone 



