1880.] MR. R. COLLET-r ON BAL/ENOPTERA BOREALIS. 203 



food; but Capt. Bull, from West Finmark, asserts that not 

 only this summer, hut in the previous ones, he found that the 

 stomach contained the so-called " Kril," which forms the chief 

 nourishment of the B. sibbaldi. This " Kril " is Euphausia 

 inermis, a Thysanopod Crustacean, about 1 h inch in length and 

 semi-transparent. It is therefore certain that the B. borealis is not 

 confined to the Copepocia for its nourishment, although the unusually 

 fine and curly, almost woolly bristles on the inner side of the baleen- 

 plates clearly show that their food consists of minute animals, and 

 hardly ever of fish. 



XIV. Habits. 



B. borealis appeared off the coast sometimes singly, but as a rule 

 in schools of different size, which might number as many as 50 

 individuals. Towards the end of the fishing-season they appeared 

 to be more broken up, after having been terrified and scattered by 

 the whaling-boats for months. 



Concerning their method of swimming, the whalers have noticed 

 some small peculiarities. During their wanderings, or when they are 

 not amongst the " Aate " {i. e. the shoals of crustaceans on which 

 they feed), they swim fast, and do not require to blow so often as the 

 other species. As a rule they blow only once or twice, whilst the 

 other kinds blow as often as five or six times during each visit to the 

 surface, and they swim for a considerable distance before they again 

 appear. Their course under the water can be traced by the bubbles 

 of air which appear on the surface. When in amongst a shoal of 

 Calanus fimnarchicus, and on the feed, they swim quite slowly, with 

 their snout and half of their back above water. The B. musculiis 

 and the B. sibbaldi under such circumstances often turn on 

 their side whilst swimming, with their mouths open to take the 

 crustaceans. 



In its temper B. borealis is inoffensive and avoids the boats. 

 But it has sometimes happened that in its death-agonies it has struck 

 the boats, and on several occasions has injured their sides or pro- 

 pellers. Such conduct has, however, probably been unintentional, or 

 committed in its agony, and cannot be considered, as it has often 

 been called, natural ferocity. 



All the whalers are unanimous in opinion that B. borealis (as well 

 as B. musculus and B. sibbaldi) can remain under water for a far 

 greater time than is generally supposed. The duration of this time 

 is estimated to be from 8 to 12 hours. Such periods of rest often 

 occur at particular hours of the day. These animals are never 

 heard to make any sound. 



XV. Value. 



The quantity of blubber as a rule is but little in this species. An 

 average-sized individual yields from 15 to 20 Norw. barrels (17 to 23 

 hectolitres) of oil ; they appear this year to have been as a rule 



