226 DISCOVERY REPORTS 



occasionally within the light grey area: most frequently, in about 15 per cent, on the 

 umbilicus and round the genital aperture (PI. XVIII, fig. 2). The under surface of the 

 flukes in 6 per cent of the whales was marked by longitudinal striations of grey on 

 a lighter background. The under surface of the flipper varies from white to light grey 

 and is occasionally almost as dark as the upper surface. 



On the dorsal surface of the body a light grey marking occurred in 8 per cent of the 

 whales. This appears as a light V-shaped area over the shoulders with the apex directed 

 forward, situated on the back above the insertion of the flippers. This marking is very 

 similar to the corresponding one present in Fin whales, but the apex of the V tends to 

 be less sharp so that the shape sometimes is closer to that of the letter U . In the foetus 

 there is a very pale area above and in front of the shoulder joint, with a very clear 

 posterior margin which crosses the humerus, but is not continued past the flipper. 



Many examples of the Sei whale are also like the Fin whale in having a white streak 

 running back from the ear for some inches in a backward and downward direction. 

 A dark mark running backwards and upwards from the posterior side of the eye also 

 frequently occurs. It appears never to be so well marked as in the Fin whale, and fades 

 into the dorsal coloration after a course of some inches or a foot in length. It was 

 sufficiently well marked to be specially noted in 7 per cent of the whales examined. 

 In these it appeared as a broad band of darker colour running up and back from the 

 eye, while there were indefinite indications of two others on each side of the posterior 

 part of the groove area, which would have formed chevron marks if they had been 

 continued to meet in the middle line. Their arms, however, merged into the general 

 body colour. 



Small light-coloured spots of irregular outline giving an appearance similar to that 

 of new galvanized iron, were found in 15 per cent of the whales examined, on the flanks 

 and side of the tail. In many cases they were so thick that the regions covered by them 

 had a light silvery grey appearance. Andrews (191 6) gives a good photograph of these 

 markings. 



In about 4 per cent of the whales a white splash on the under surface of the anterior 

 border of the maxilla, similar to that frequently present in Humpback whales, was 

 observed. 



The distribution of the colour in the Sei whale is usually symmetrical, or at least 

 not markedly asymmetrical, though the margins of the pigmented and unpigmented 

 areas are irregular and indefinite. In about 10 per cent the coloration was definitely 

 asymmetrical, the whole of the pigment being shifted slightly to the right as in the Fin 

 whale. The asymmetry becomes specially evident in those individuals in which the 

 white area on the ventral grooves is considerably restricted laterally, so that a narrow 

 strip of white occurs on the grooves, the greater part of it on the left side of the median 

 line. If, as appears likely, the asymmetrical coloration of the Fin whale is associated 

 with the habit of swimming and feeding slightly on the right side, a similar association 

 would be expected in the Sei whale, though Millais (1906) states definitely, and 

 emphasizes his statement with italics, that when feeding this species does not turn on 



