THE WHALEBONE WHALES OF THE WESTERN NORTH ATLANTIC. 



221 



third was shining black, btit the remainder all snow-white. The anterior border 

 was thick and nmnded, but irregularly eniarginated and covered with numerous 

 examjiles of CoronuJa diadema ; the hind mai-gin sharp and entire. 



"The dorsal fin was shining black. 



"The flukes were black on the upper sui'face, with a number of scattered, 

 irregular snow-white spots ; on the lower surface, the ground color of which was 

 shining black, these snow-white spots were more numerous. The anterior boixler 

 of the flukes was thick and rounded, the posterior mai'gin, strongly emarHnate and 

 occupied by many examples of Goronida diadema. 



" The whalebone was all gray-black." 



Eawitz (7.^, 89) states that the whalers account for the variation in color on 

 the basis of difference of age. "They say that young animals have a black ventral 

 skin, and the old ones a white skin ; the formei' have little l)lubber and the latter 

 much." He is inclined to accept this explanation, as the four specimens he exam- 

 ined seem to support it. He remarks : " We should have then, were this explana- 

 tion correct, the highly interesting physiological phenomenon before us, that with 

 increasing fat in the corium (^itnterhavt), the pigment in the epidermal cells 

 completely disappears." 



In order to test this theory I have arranged below the 13 specimens from dif- 

 ferent parts of the Nt)rth Atlantic in the order of size, the smallest first. In the 

 table, the letter W signifies that a part is white, V signifies that it is varied, part 

 white and part black, and B signifies that it is entirely black, or substantially so. 



Assuming that the thirteen specimens belong to the same species, the fore- 

 going table lends some support to Rawitz's theory, as the youngest specimens all 

 have the throat, breast, and belly entirely black. It will be noticed, however, 'that 

 my Newfoundland females, which were adults, were but little white, so that it 

 would appear that whiteness is not invariably assumed by mature individuals, and 

 may be rather a sign of senility. There is probably a considerable individual 

 variation in this regard, as there certainly is in other genera. Rawitz's largest 



