272 Proceedings of the Royal Physical Society. 



shot, in which I found in one ovary of each a large false 

 corpus luteum, which I judged was about two weeks old ; 

 they were i to -f- inch in diameter. This suggests that 

 another rutting period occurs about the month of August : 

 neither of these bears were gestating. Very young cubs 

 were only seen in February and March, older cubs were to 

 be seen at the end of winter. In one case we obtained a cub 

 under one week old in a hibernating hole on 3rd February. 

 From this fact, and from seeing the two together early in 

 March, it would suggest that the gestation period was 

 between ten and eleven months. Cubs seem to continue 

 with, and be suckled by, their mother for nearly two years. 



The very young cub referred to had its eyes open. The 

 weight of twin cubs, shot on 15th January, was 234 lbs., and 

 were judged about a year old; milk was in their mother's 

 mammae, and freshly killed seal in their stomachs. Twins 

 are perhaps most frequent. 



I do not consider that the Polar Bear hibernates. Out of 

 one hundred and nineteen adults, and about five cubs, forty- 

 three, or more than one-third of the whole, were met during 

 the Arctic night of four months. Had it been light, more 

 would have been seen, hence the statement that " in the most 

 northerly wintering places of ships, the bears almost com- 

 pletely disappear," ^ must be refuted. Again, it is said ^ the 

 thymus gland exists throughout life, and enlarges every 

 hibernation in hibernating animals. But I have never 

 found the thymus gland in an adult bear, not even when 

 actually in a so-called hibernating hole. Payer,^ quoting 

 Kichardson, says: "it is only pregnant females who hiber- 

 nate in a snow-hole, while the males roam over the Arctic 

 Seas in search of places free from ice." My list shows that 

 during the winter months almost the same number of females 

 were seen as during the summer months. That pregnant 

 females do not necessarily hibernate is supported by the fact 

 that we shot one, with twin foetus two to three months old, 

 on 6th December, after forty-seven days of the Arctic night, 



1 *' Royal Natural History" (Lydekker), vol. ii. p. 5. 



2 Kirkes, "Handbook of Physiology," 1892, p. 521. 



^ "New Lands within the Arctic Circle," vol. ii. p. 107. 



