1886.] MR. R. COLLETT ON BALZNOPTERA BOREALIS. 263 
food; but Capt. Bull, from West Finmark, asserts that not 
only this summer, but 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 13 inch in length and 
semi-transparent. It is therefore certain that the B. borealis is not 
confined to the Copepoda 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. Hahits. 
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”’ (7. e. the shoals of crustaceans on which 
they feed), they swim fast, and do not require to blow so often as the 
other species. Asa 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 finmarchicus, and on the feed, they swim quite slowly, with 
their snout and half of their back above water. The B. musculus 
and the 2B. 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. sibéaldi) can remain under water for a far 
greater time than is generally supposed. he 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 
