CO885-(23-24) — Page 201

APPENDICES.

77

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would seem to be the principal seat of growth in the humpback bull. In the adult females these dimensions do not show a corresponding decrease in value: in fact, Dimensions 2 dimensions 12 and 18 tend to lengthen with advancing maturity. and 3 show that the degree to which the mandibular symphysis projects beyond the tip of the snout is subject to greater variation in the female than in the male, although the average projection is less in the former sex than in the latter. The pectoral is shorter relatively in the adult females than in the sexually immature females; in the males its relative length appears to increase with maturity: the growth of the pectoral would, therefore, seem to be limited in the female and relatively persistent in the male.

As stated above, True's measurement of the total length differs from that used by Major Barrett-Hamilton at South Georgia, but many of the other North Atlantic measurements were similar to those made at South Georgia, and the effect of the slight difference upon the percentages given in the above table is, as True himself pointed out, far less than might have been supposed.

Dimension 6.-The distance between the tip of the snout and the centre of the eye agrees in average relative value in the humpbacks of the North Atlantic and those of South Georgia; in the latter, however, the observed range of variation in this respect is greater, especially in the males. In the Pacific form (M. versabilis, Cope) this dimension appears to be considerably shorter.

Dimension 7-The distance between the tip of the snout and the centre of the blowhole is distinctly greater relatively at South Georgia than in the North Atlantic; the northern measurements were probably made, in most cases, to the anterior margin instead of to the centre of the blowhole, but, making the utmost allowance for this difference, the distinction between the northern and the southern stocks in this respect is still apparent. With the exception of one case--in a male 44 ft. 9 in. long, captured off the coast of Iceland in 1867 (Hallas, Vid. Med. Nat, For. Kjöben- havn, 1888, p. 176)-no northern value exceeds that of the South Georgian minimum. In the Iceland specimen this dimension was, in fact, relatively greater than in any measured at South Georgia; this whale may have been a wanderer from the southern ocean. M. versabilis, Cope, agrees with the North Atlantic form in this respect.

Dimension 8.-The distance between the tip of the snout and the axilla aver- ages about 4 per cent. greater at South Georgia than in the North Atlantic; the maximum value for the north is distinctly below the average for South Georgia. This dimension was not recorded for the Icelandic specimen mentioned in the last paragraph. Scammon's measurement in M. versabilis is extremely short, but it may have extended only to the foremost edge of the pectoral insertion instead of to the axilla.

Dimension 9.-The distance between the centre of the eye and the ear was measured only in the female No. 206; this dimension was relatively a little shorter than in the male from Belmullet, Ireland, and a little longer than in a female of M. versabilis measured by Scammon.

Dimension 10.-The distance between the tip of the mandible and the angle of the gape averages about 6 per cent. greater relatively at South Georgia than in the North Atlantic, and nearly 9 per cent. greater than in M. versabilis, Cope. In only one instance from the north-a female, 46 ft. 5 in. long, from Bear Island (Rawitz, Arch. f. Naturgeschichte, 1900, (1) p. 78)—was this dimension equal in value to the minimum observed at South Georgia.

Dimension 11.-The distance between the notch of the flukes and the anus averages a little less relatively at South Georgia than in the North Atlantic. True cites Sars's measurement as the maximum for the latter region, and gives it as 25-8 per cent. of the total length; there is some error here because Sars gives the dimen- sion as 3.05 metres, which is 21.5 per cent. of the total length. In M. versabilis this dimension appears to be more than 2 per cent. longer relatively than at South Georgia.

Dimension 13.-The distance between the notch of the flukes and the navel also averages a little less at South Georgia than in the North Atlantic; the observed range of variation, particularly in the males, is, however, much greater at South Georgia.

Dimension 18.-The height of the dorsal fin averages very slightly less at South Georgia than in the North Atlantic.

Dimensions 17 and 18.-The pectorals are slightly shorter and slightly broader at South Georgia than in the North Atlantic. Judging from Scammon's measure ments the humpbacks of the Pacific are quite remarkable for the shortness and the narrowness of their pectorals; this character was one of those relied upon by Cope when establishing his M, versabilis.

The differences noted above seem to indicate that the humpbacks of South Georgia have relatively longer heads, with larger mouths, than have those of the North Atlantic. Attention is called to this point later on when discussing bellicosa," Cope, in connexion with the questions relating to migration.

FURTHER NOTE ON BODY MEASUREMENTS.

++

M.

Since the above section of this report was written I have found it possible to arrange most of the humpbacks examined at South Georgia in three groups. These groups are characterized by differences in the colour of the belly, and, judging from Major Barrett-Hamilton's notes and the earlier statement of Mörch (dealt with below under "Colour"), they must be fairly well defined. While working up the notes relating to breeding and migration it appeared to be desirable to pursue this matter a little further, and I have therefore re-examined the measurements and have drawn up the following table in which the three supposed races are contrasted. List and lengths of sexually mature humpbacks from South Georgia classified according to colour :--

(1) White-bellied.

Males: Nos. 31 (40·3 ft.), 70 (45-75 ft.), 212 (45-5 ft.); no body measurements

given of Nos. 70 and 212. Average length of 3=43.85 ft.

Females: Nos. 151 (47 ft.), 189 (43·5 ft.), 217 (49-5 ft.). Average length of

3=46.66 ft.

(2) Marble-bellied.

Males: Nos. 7 (38 ft.), 17 (42 ft.), 27 (42 ft.), 182 (45-75 ft.), 226 (44 ft.); no body measurements are given of No. 226. Average length of 5-42-35 ft. Females: Nos. 13 (47 ft.), 14 (49-75 ft.), 48 (45 ft.), 69 (43-5 ft.), 94 (42 ft.), 106 (46.5 ft.), 223 (52 ft.); no body measurements are given of No. 69. Average length of 7-46-53 ft.

(3) Black-bellied.

Males: Nos. 53 (495 ft.), 57 (455 ft.), 62 (45 ft.), 162 (44-5 ft.); no body

measurements are given of No. 62. Average length of 4-46.1 ft. Females Nos. 54 (43-75 ft.), 59 (45-5 ft.), 126 (48 ft.), 152 (46 ft.), 153 (48 ft.), 206 (42 ft.), 251 (45 ft.), 260 (48 ft.), 288 (45 ft.); no body measurements are given of No. 59. Average length of 9=45-7 ft.

In the following table the body measurements are given as percentages of the total length :-

HUMPBACKS of South Georgia.

2. Projection of tip of mandible

beyond tip of snout:-- Immature males

females

White-bellied.

Marble-bellied.

Black-bellied.

(1) 5-88

Average and range in mature males

12

19

females

(1) 8·05 (1) 5-7 (8) 4-26, 8·72—5·05

(2) 1·82—5-68

(8) 3·42, 2-88—5.26

(4) 2-48, 0—8.87or

(8) 3-31, 2-88-8-87

6. Tip of anout to centre of eye :-

Immature males

females

Average and range in mature males (1) 28

females | (2) 284, 21·9—22-9

71

7. Tip of out to centre of blow-

hole:-

Average and range in mature males

19

*

"

females (1).22-9

(1) 29.5

(8) 23-6, 22-4-26-2 22·6, 22-2-28-1

(2) 2·86-4.69 (8) 8-27————4-84 (1).4.5

(7) ·88, 2·78—5-2

(2) 18-6-80-7 (8) 29--28-1

(9) 24·6, 20-9--28-8

24·6, 29·9--25

(1) 23·8

(8) 21·3, 20·8—22·9

78

APPENDICES.