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142
APPENDICES.
Professor Guldberg estimated the length of the ripe fœtus to be probably about 7 to 7.5 metres. On account of the great size of the foetus he thought one could assume with certainty that the period of gestation was longer than twelve months; earlier, judging from the report of a lecture which appeared in "Vardö Posten," 2nd September, 1883 (of which report a translation is given by Mr. Cooks, Zoologist, 1885, 17), he appears to have thought that gestation lasted from eighteen to twenty months. Pairing taking place at various times, the time of parturition was believed to be equally indefinite. Professor Guldberg showed that parturition might some- times happen at Finmark in the summer; an old female was brought into Vardö in the first week of July; she was in milk, and the condition of her womb suggested that she had given birth to a calf shortly before.
The blue whale which stranded at Longniddry, Firth of Forth, on 3rd November, 1869, contained a fœtus 19 ft. 6 in. long. Sir William Turner thought this fœtus to be nearly ready for birth and supposed this species to give birth to its young
in the late autumn. In support of this view he cited Coughtrey's state- ment that in October, 1869, the latter saw a blue whale floating dead, her mammæ full of milk, and with her a new-born calf, about one-fourth of her length, and por- tions of the foetal membranes; this dead whale was seen off Northmaven, Shetland. With regard to the Longuiddry fœtus, Professor Guldberg was of opinion that it still wanted some feet in length before it would be ready for birth; and with regard to the Northmaven whale he asked whether this case was not really, perhaps, a post- mortem birth brought about by the expansion produced by the gaseous products of decomposition in the abdomen or by the shock of the dam's death.
Professor Guldberg pointed out that the calf follows the mother until it is at least half grown; that the mother becomes lean after suckling for a while; and that He a female still accompanied by a calf 40 ft. in length had been seen pairing. concluded that the dam does not give birth to a calf in each year. He conjectured that the young may be born in warmer latitudes near the North American coast. The winter quarters of the blue whale were unknown, but Guldberg was inclined to believe they were off the coast of North America; one caught by Svend Foyn, in 1879- 1880, had a harpoon of a type used in America sticking in it. The sailors told Guldberg that great numbers of blue whales occur off the coast of Iceland in the spring, and that subsequently these go east towards Norway.
The accounts of the breeding habits of the blue whale given by Professor Collett and Mr. Mörch follow that of Professor Guldberg in the main. Both writers agree that there appears to be no fixed time for pairing or parturition, and that though pairing is often observed off the Finmark coast in the summer (July or August) it takes place at other times also. Collett states that about half of the adult females which have been caught off the Finmark coast have been pregnant; that since most of the females captured during July and August have contained foetuses of from 3 to 9 ft. long (or less) the pairings for them must have happened in the winter or spring; that the fœtuses examined at Finmark date mostly from the months June to August, those of the first part of this period being of small average size, while those of August are half-grown or large; but he points out that large and small foetuses can Both Collett and Mörch be found contemporaneously throughout the summer. merely state that "it is assumed " that the period of gestation is more than twelve months. Collett states that some of the young are born at Finmark; that occasion- ally they have been born there in August, "but the majority of the individuals leave our waters in the autumn before the time for parturition in order to give birth to their young
in the autumn or winter months far from Norway in the western parts of the North Atlantic." On the other hand, Mörch says that these whales have never been seen at Finmark with small calves, though they have been seen occasionally with larger ones; he adds that, although it is believed that there is no fixed time for birth, this probably takes place in American temperate waters, and that the American Sulphur Bottom variety has occasionally been observed in Finmark waters.
Collett states that the young follows the mother till it has attained a length of from 40 to 60 ft. At Ireland, in the summer of 1903, a calf 63 ft. long, which still sucked, was killed; but since the stomach of this calf contained Crustacea as well, it was evidently about to be weaned. Burfield records a suckling 50 ft. long, which ac- companied its dam, 83 ft. long, the latter being captured on 14th July, 1911, at Bel- mullet, Ireland; the Norwegians supposed this calf to be not more than one year old, and they think calves remain with their mothers for about one year. Captain Horn (in Cocks) mentions two calves, one between 50 and 60 ft. long, the other 40 ft. long, which were captured with their mothers at Finmark in July, 1886.
APPENDICES.
143
I have recorded in the table at p. 140 all the data known to me concerning the fœtuses of the blue whale from the North Atlantic and from South Georgia. This available information has been very carefully examined with a view of determin- ing, if possible, the nature, duration and time of the sexual season of this species in each hemisphere.
The smallest foetus of which the sex is recorded is a female 597 mm. long, examined by Major Barrett-Hamilton at South Georgia, on 18th December, 1913. Professor Guldberg mentions a male and female foetus each 660 mm. long, from Finmark, obtained on 22nd and 28th June, 1883, respectively. One may, perhaps, fairly assume that the general form, including the external genitalia, of the foetus of the blue whale is perfected by the time its length amounts to 500 mm.; and I do not think that such a fœtus can be less than three months old.
I have taken 7,500 mm., the higher figure given by Guldberg, as being the approximate length of a new-born' blue whale; the length by which the foetus is increased after its preliminary development to 500 mm. may therefore be regarded as 7,000 mm.
After a good deal of reflection, I am inclined to think that there is no good reason for supposing, with Professor Guldberg, that the period of gestation is sub- As mentioned above, Guldberg's first stantially longer than that of the finner.
view was that the gestation of the blue whale lasted for from eighteen to twenty months; later, he contented himself with saying that it certainly lasted longer than twelve months. The only reason I can find for supposing the period of gestation to be longer in the blue whale than in the finner is in the fact that the foetus of the former is larger than that of the latter. But this does not necessitate the assump- tion of longer gestation, because the finner is only about four-fifths of the size of the blue whale, and this is true not only of adult individuals, but of the new-born calves also, as the following comparative table demonstrates :—
Females:-
COMPARISON of the LENGTHS OF THE Blue Whale and the FinneR. (South Georgia: Major Barrett-Hamilton's measurements.)
བཧྨསྒྱུ =
Blue Whale.
Finner.
84%.
= 83.5%
= 86.8°/
Males:-
Maximum
91
Average length of sexually mature Smallest sexually mature
80-2
ft. 100 = 100
74
= 100
11
72 {t. = 79% 67.15 61.75
Maximum
95
31
= 100
82
1E
Average length of sexually mature
88-4
11
= 100
71.8
11
= 81.2%
Smallest sexually mature (75 ft.-80 ft.)
77.5
11
= 100
61
"
= 78.8%.
Foetuses (North Atlantic):--
Length at birth
7,500mm. 100
6,100mm. 81·8%
100
82%
Average length in both sexes at all stages of growth
Supposed increase of length of fœtus during the last
nine months of gestation Average daily increment
7,000mm. 100 25.7mm. 100
5,800 83% 21.25
83.
**
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The above table shows that in assuming that the development of the fœtal blue whale from a length of 500 mm. to 7,500 mm., or birth, occupies a period of nine months, I postulate a rate of growth which, having regard to the difference of size subsisting between the two species, is practically equal to the rate of growth which I have assumed above in the case of the fœtal finners.
The ages of the blue whale foetuses and the possible dates of the pairings for them, have been calculated as follows:-
7,500 mm. - 500 mm. = 7,000 mm.
7,000 mm. the observed length of the fœtus minus 500 mm. : : 273 days : number of days of growth subsequent to the completion of the pre- liminary development.
Age of foetus days of subsequent growth, plus 91 days of preliminary
development.
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