THE WHALEBOKE WHALES OF THE -WTESTERN NORTH ATLANTIC. 121 



it is all dark (blue-black), but on the right side, as Schlegel has stated, the foremost 

 is of a light yellow-white color. 



"The bristle-like fibres, into which the whalebone resolves itself on the inner 

 side, are uniform yellow-wliite on l)oth sides [of the mouth]." 



All these peculiarities of color were observed in specimens taken at Snook's 

 Arm, Newfoundland, in 1899, namely (pis. 8 to 11), the narrow inferior white 

 caudal maigiu, the antero-infei'iorly-directed, narrow, dark mark reaching forward 

 to the anus, the areas of dark color below the root of the pectoral, the white mark 

 anterior to the root of the pectoral, with its streaks directed forward and back- 

 ward, the dark-streaked white anterior border of tlie pectoral, the white light 

 lower and uppei- jaws, and whitish anterior right whalebone. In no two indivi<Iu- 

 als, however, were the amount and disposition of the dark color precisely the same, 

 while the want of uniformity of color on the two sides of the body was always 

 conspicuous. As in land animals, there were veiy pale individuals and very dark 

 individuals, and others which re[)i'esented neither extreme. In some the inferior 

 caudal margin was entirely dark forward to the anus, and very large dark areas 

 invaded the white of the belly, while the inferior surface and anterior white 

 margin of the pectorals were streaked with dark color, and all light markings were 

 restricted and obscured. In other specimens the white infei'ior caudal margin was 

 broad and the postanal dark mai-ks indistinct; the dark color hardly passed below 

 the level of the pectorals, leaving practically the whole belly white, and the white 

 markings about the base of the pectorals were large and distinct. 



In the midst of these variations, however, the presence of a dark left lower 

 lip (pi. 11, figs. 3 and 4), white right lower lip, and white anterior right whale- 

 bone remained constant, and the right side of the body never carried so much 

 dai-k color as the left. This peculiar asymmetry of color, or " pleuronectism," 

 was first pointed out by Sars in 1878. Guldberg has more recently asserted that 

 it is not exclusively confined to one side, or, in other words, that an individual 

 miiiht be lio-ht on the left side and dark on the right side. My own observations 

 on American specimens do not bear out this statement. The right side in these 

 was always lighter than the left side, and I am disposed to think that this is a 

 constant character of the species. (See pi. 9, fig. 3; pi. 10, figs. 1 and 3; pi. 12, 

 figs. 1 and 2.) 



VARIATION IN COLOR OF BODY. 



The individual variation in the amount and disposition of the white and gray 

 colors of the body has already been referred to. It may be of interest to enumerate 

 the differences in some of the Newfoundland Finbacks, from notes made on fresh 

 specimens. 



In ten specimens the variations were as follows : 



No. 2. Female. Length, 64 ft. 8 in. General color dark. Below the left 

 pectoral 35 furi-ows in the direction of the median line are dark colored. The 

 remaining median furrows are white, with a flesh-colored tinting. Left mandible 

 and upper jaw dark gray. The former whitish internally. Beginning at the 



