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CETACEA—LILLIE. 111 
These regular migrations, which are described here probably for the first time, 
have been known to New Zealand whalers for many years, and they adjust their 
headquarters in accordance therewith. In the winter, whaling operations are carried 
on from the Bay of Islands; and in the summer from Campbell Island, in the 
Sub-Antarctic. The plankton samples taken on board the ‘Terra Nova” during 
her three summer voyages from New Zealand to the Ross Sea, and by Mr. Nelson 
at the winter quarters in McMurdo Sound, tend to show that there is considerably 
more food for Whalebone whales in the cold Antarctic waters than in the warm 
seas to the north of New Zealand. Diatoms were so abundant in parts of the Ross 
Sea, that a large plankton net (18 meshes to an inch) became choked in a few 
minutes with them and other members of the Phytoplankton. It is extremely 
probable that m such localities whales feed upon the plants as well as the animals 
of the plankton. Moreover, as whalers are only too well aware, the blubber is 
appreciably thicker when the animals are leaving the cold waters than it is when 
they are on their way South after their sojourn in the sub-tropics. 
It would therefore seem unlikely that the migration of Humpbacks from South 
to North in the winter can be caused by the search for food. .It is far more 
probable that this journey is undertaken for the purpose of parturition, in order 
that the calves may be born in congenial climes. The latter motive received 
support from the fact that mothers, with newly born calves, were constantly to be 
seen off the Bay of Islands after the beginning of July. On July 24, 1912, a female 
was shot, from which I obtained a foetus 133 feet in length. The length of the 
calf at birth is about 15 feet in this species. 
On October 10, 1912, I found a foetus 24 inches long, and possibly three months 
old, nm a female which was killed while on her way southward. 
Foetuses of intermediate length have never been seen by Mr. Cook, during the 
twenty years he has been at the Bay of Islands. 
The above data suggest that parturition, and possibly copulation, take place in the 
warm seas during the Southern winter ; and that the mother carries the calf throughout 
her summer visit to the Antarctic Ocean. The period of gestation in this species 
is either about twelve or twenty-four months, according to whether the mother 
carries the calf for one, or two seasons. Several young, unpregnant females were 
seen at the Bay of Islands, which showed that the northward migration was not 
confined to females in the last stages of pregnancy; and the apparent absence of 
foetuses of intermediate size, at the New Zealand Whaling Station, tends to support 
the shorter estimate for the period of gestation. 
From information given to me by whaling captains, who have worked at their 
trade in various parts of the Southern Hemisphere, and whose veracity of statement 
I have tested and found to be reliable, it appears that similar migrations of 
individuals of this species are known to take place off the shores of South America, 
South Africa, Tasmania, and Australia. This evidence tends to show that in the 
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