KUNGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 40. N:0 5. 35 



towards the anterior börder of the inner side, the outer side being of the same 

 colour as the upper parts of the body, that is blackish. The lower side of the cau- 

 dal flukes is also white with scattered blackish spöts. 



Racovitza' s (18) description of the colour of the Humpbacks observed by him 

 does not quite agree with this. Although he has only seen the whales in the water 

 it must be kept in mind that he has seen them on close quarters and has had good 

 opportunities to study them so that he gives quite detailed descriptions. He says 

 that the upper parts were black but the throat and belly white. The pectoral fins 

 he found to be, to a great extent, white, below always white, »the upper parts often 

 spotted with black. » The ventral parts of the caudal region varied, according to 

 Racovitza, (18) very much in colour, being sometimes/ but seldom, quite black, or 

 quite white, usually spotted with white and black in variable degree in each indi- 

 vidual. 



Against Racovitza's description Sörlltstg has emphasized that none of the 75 

 specimens he saw on land had anything white on the outer side of the pectorals and 

 hardly ever any white on the under surface beyond the pectoral arch. 



Once Racovitza (18) saw an albino specimen, ivory-coloured above and white 

 beneath. The question now remains how to explain the stränge discrepancy between 

 the reports of Racovitza and Sörling concerning their observations about the colour 

 of the Humpbacks seen by them. This discrepancy is namely too great to be dis- 

 regarded, as both observers, of course, are fully trustworthy. I think there is no 

 other way out of this difficulty than to assume that the whales seen by the two 

 observers ha ve belonged to two different geographic races with, to some degree, 

 different colour. It is then to be remembered that Racovitza (18) has studied the 

 Humpbacks chiefly in the waters to the west of the Graham land mäss, (except 

 some few seen in the Beagle Channel) and this area belongs naturally to the Pacific 

 Ocean, whereas Sörling's field of observation at South Georgia belongs to the 

 South Atlantic. It is not impossible that the Humpbacks of the southern part of 

 both oceans belong to different herds or stocks which do not mix and have not done 

 so for ages, if not exceptionally. In such a case two separate geographic races with 

 some differences in colouration may have originated. 



It is interesting to note that this difference is parallel to that between the 

 Humpbacks of the northern and those of the southern Atlantic. The colour of the 

 former is certainly variable, but, unlike the southern atlantic race, the northern has 

 according to all authorities the pectoral more or less white on the upper or outer 

 side, as well, and the white markings on the under surface of the body appear to 

 extend further backwards, at least in many specimens. The colour of the northern 

 atlantic Humpbacks thus agrees better with Racovitza's observations of the Hump- 

 backs west of Graham land than with Sörlincts at South Georgia. The young spe- 

 cimens in the North Atlantic are, however, as a rule darker with blackish throat 

 and breast than the adult. 



The furrows of the South Georgia Humpback have the same colour as the 

 suiTounding parts. 



