42 



DISCOVERY REPORTS 



tonic diet is started and the baleen becomes functional. The stomachs of the two young 

 whales with baleen i8 cm. long contained a yellow substance which was probably partly 

 digested milk, and certainly was not krill, so that they may be counted as sucking calves, 

 a conclusion that is supported by the baleen length and its position in this figure. 



Only one record of the width of the baleen is available, from a male whale 9-83 m. 

 long. In this the baleen was 43 cm. in length and 12-5 cm. in width, the width being 

 29 per cent of the baleen length. In Fig. 43 the spacing of the baleen plates is plotted 

 against the length of the whale and shows a regular increase with length and no sexual 

 or racial differentiation. 



Total Length in metres 



Fig. 43. Humpback whale. Spacing of baleen. 



POSSIBLE DIFFERENCES BETWEEN NORTHERN 

 AND SOUTHERN RACES 



In none of the characters considered above can any constant differences from those 

 of Humpback whales taken in the northern hemisphere be detected. It would appear 

 that every point that has been used hitherto in differentiating races, subspecies or species 

 of Humpbacks comes within the range of normal variation when a full series of speci- 

 mens is examined. Some of the measurements of body proportions that have been thus 

 used are shown above to be functions of length, and therefore useless as racial criteria 

 unless specimens of similar length are compared, which has not been done. Hinton (1925) 

 shows that there is no real difference in length between Humpbacks of the northern and 

 southern hemispheres. He also says that in the south the females outnumber the males, 

 whereas the opposite is the case in the north, a statement which is not borne out by 

 fuller evidence, at least as far as the south is concerned. The only difference that can be 

 found between the whales of the north and the south is a physiological one : the dif- 

 ference in the time and direction of their migrations and in the time of their breeding 



