40 DISCOVERY REPORTS 



outer grooves run to the edge of the mandible, so that a median ridge is formed below 

 the chin. This is noted by Struthers (1889), who compares it to a second chin, and later 

 authors have sometimes referred to this protuberance as the "cut-water". In conse- 

 quence of the median grooves stopping short of the chin a number of short grooves 

 anastomose on each side, giving the appearance, as noted by Millais (1906), of crossing 



like tramlines. 



BALEEN 



The baleen of the Humpback whale is very coarse in texture, with coarse bristles at 

 the inner edges of the plates. The colour of the plates varies from grey to almost black, 

 and the bristles are white to greyish white. In many specimens some of the anterior 

 plates or their outer edges are white. When white plates are present together with a 

 white splash on the side of the snout, as described above, the position of the white plates 

 corresponds with that of the white splash. For example whale no. 793, a male, had 

 thirty-five white and partly white plates on the left side and thirty-eight on the right, 

 corresponding in position with white splashes on the snout. White plates may, however, 

 be present when the splash is absent and vice versa. Struthers (1889), also quoted by 

 True (1904), records the occurrence of white plates at the anterior end of the series. 



The records of only two counts of the number of plates are available, one from a male 

 8-4 m. long with 320 plates on the right side and the other from a female ii-8 m. long 

 with 361 plates on one side. Hinton (1925) gives a count made on a humpback 7-44 m. 

 long at South Georgia of "about three hundred plates on each side". Millais (1906) 

 counted three hundred and twenty-five plates on each side in a northern Humpback at 

 the Shetlands, a figure which agrees with the present data, but quotes Scammon as giving 

 five hundred and forty plates in a female 52 ft. (approximately 16 m.) long, which would 

 mean only two hundred and seventy plates on each side. With this may be compared a 

 record made at South Georgia by the late Major Barrett-Hamilton and published by 

 Hinton (1925) of a female Humpback 13-93 m. long with " about two hundred and fifty 

 plates on each side ". True (1904) gives no first hand counts of baleen plates in northern 

 Humpbacks, but quotes Eschricht as giving "about four hundred plates on each side" 

 in Greenland Humpbacks. 



Fig. 42 shows the length of baleen plotted against the total length of the whale. With 

 the figures of the present series are included eight measurements of baleen taken at 

 South Georgia in the season 1913-14 and published by Hinton (1925). The baleen varies 

 from 18 cm. in length in a whale 7-25 m. long to 107 cm. in length in a whale 14-66 m. 

 long, thus agreeing with the recorded data (Struthers, 1889; Millais, 1906; True, 1904) 

 regarding the northern Humpback. The solid line in the figure represents the growth 

 curve of the baleen as obtained from the plotted points, the dotted portion represents 

 the growth in the foetus and calf and joins the smallest measured baleen to the origin, 

 which is somewhere above a foetus-length value of 0-84 m., because none of the foetuses 

 examined was greater than that length, and in none of them was there any trace of 

 developing baleen. The sudden spurt in the growth of the baleen between the lengths 

 of 7 and 8 m. represents the accelerated growth at the time of weaning, when a plank- 



