313 DISCOVERY REPORTS 



instance, they are generally very small just behind the eye and relatively larger along 

 the posterior part of the flanks. In individuals in which these marks are in general 

 small they are usually relatively sharply defined, while in other individuals they are 

 bigger and more difl^use, in which case they often coalesce to a large extent and may 

 occupy actually more space than the dark background. In others again they may be 

 of medium size and if very numerous run together so as almost to obliterate the darker 

 colour. Plate XXVIII, fig. 2, gives an example of a whale in which the spots are 

 moderately large, very numerous and coalescing to an unusual extent. 



These pale spots may also be seen here and there on the ventral grooves, where, 

 however, they are less noticeable than on other parts of the body. On the ventral 

 grooves there are almost invariably a number of white flecks more or less similar in 

 size and shape to the pale bluish spots. The numbers in which these spots occur con- 

 stitutes the most marked feature of the variations in the pigmentation of Blue whales. 

 A typical or average condition is shown in Plate XXX, fig. i, but Figs, i, 2 and 3 in 

 Plate XXIX and Figs, i , 2 and 3 in Plate XXX form a series which illustrate the range of 

 variation. These white flecks tend to be grouped on each side towards the posterior end 

 of the ventral grooves. They are usually also fairly numerous beneath the flipper on 

 each side and are sometimes even more plentiful here than at the posterior end of the 

 ventral grooves. In extreme cases there may be hardly a white fleck anywhere, as in 

 Plate XXIX, fig. I , or the whole grooved area behind the flipper region may be a mass 

 of white as in Plate XXX, fig. 3. On the whale illustrated in this photograph the flecks, 

 though very numerous, were not very sharply defined and had to some extent coalesced so 

 as to produce a cloudy white effect. PlateXXIX,fig. 3, and Plate XXX, figs, i and 2, show 

 intermediate conditions. The flecks shown in Plate XXIX, fig. 3, are mostly grouped 

 further forward than usual, whilst these shown in Plate XXX, fig. 2, are concentrated well 

 back and to each side. Not infrequently there is a white splash over the umbilicus as in 

 Plate XXX, fig. 3. The white flecks sometimes extend behind the umbilicus, and cases 

 have been recorded in which the white has coalesced on each side of the umbilicus to 

 form a pair of transversely placed, elongated white patches which are usually, but not 

 always, symmetrical (see Plate XXXI, fig. i). 



Slightly pitted white spots occur frequently on the flanks and tail region, but these 

 are healed scars and will be considered separately in another section (p. 373). 



The flippers are pigmented over the greater part of the outer surface, but have little 

 and sometimes no pigment on the inner, or ventral, surface. There is a certain amount 

 of individual variation here. A common condition is that shown in Plate XXX, fig. i, 

 where there is a streak of pigment running from a point near the apex of the flipper, 

 forwards to about the middle of the inner surface and a small patch curving over the 

 anterior part of the lower border from the outer surface of the flipper. Frequently, 

 however, the inner surface is pure white. An example of this is shown in Plate XXVII, 

 fig. I . In this whale the flipper has been almost cut in half and the distal part turned 

 forward so that the inner surface is shown. In other cases, which are not very common, 

 almost the whole of the inner surface is covered with streaky pigment (see Plate XXXI, 



