424 AGE-PHASES OF THE RORQUAL. 



left the Faroes, the few that remain being restless and evidently 

 on the move. 



The most important item in this statement is, however, that 

 these Rorquals arrive off Finmarken in two divisions, the first of 

 which is composed of members of the dark phase — which I presume 

 to be represented by the above-mentioned dark-tailed specimen. 

 These dark whales arrive early in March and advance in an 

 easterly direction, but do not, as a rule, go beyond the Yaranger 

 Fiord, whence they return in the middle of April along the coast ; 

 the migration being completed by the end of the labter month. 



The second division consists chiefly of the two lighter-coloured 

 phases, which I take to correspond with the light-tailed form 

 described by Prof. Collett. N^othing is said as to the nature of 

 their food; but it seems highly probable that it is this light- 

 coloured phase which is taken off Mayo feeding on shrimps, &c. 

 The members of this second division reach the Faroes in the first 

 half of June, and are then met with about fifteen miles off Sorb, 

 where they stay till about the beginning of July, when they move 

 eastwards as far as Baadsfiord, whence they finally disappear in 

 a north-easterly direction. 



Schools composed chiefly of the light-coloured and yellow phases 

 reach Spitzbergen in the middle of June and move on towards the 

 north-east ; returning along the coasts of Spitzbergen from about 

 the end of July, and disappearing by the middle of August. 



The existence of one dark and two lighb phases of this Rorqual 

 being thus cleai-ly established, and it being also known that the 

 dark phase is the one associated with herring-shoals, it remains 

 to account for these differences. One explanation would be that 

 we have to do with distinct races ; but although such an explan- 

 ation might be entertained if we had to do with two phases only, 

 it is difficult to accept when there are three. The alternative is 

 to regard the three colour-phases as representing differences in 

 age. Cetaceans of many kinds are known to show considerable 

 variation in colour according to age ; a notable instance being 

 afforded by coloured casts of two Norwegian examples of Sowerby's 

 Beaked Whale [Mesoplodon hidens) exhibited in the whale-room at 

 the British Museum. In the smaller of these the belly is pinkish 

 yellow, whereas in the larger example it is as black as the back. 

 So different, indeed, are the two specimens, that I at one time con- 

 sidered they might be specifically distinct. I believe, however, 

 that Norwegian natuialists regard the black-bellied phase as the 

 fully adult condition of the white-bellied form ; and if this be 

 correct, there is every reason for regarding the colour-phases of 

 the Rorqual as being likewise dependant upon age. Assuming the 

 colour-changes of the Beaked Whale to be paralleled in the Rorqual, 

 the dark phase of the latter should be the oldest ; and that this 

 is the case is indicated by the skeleton of the aforesaid specimen 

 in the British Museum, which is that of a very old individual, as 

 is shown by the complete welding of the epiphyses to the centra 

 of the vertebra?. It may be also confirmed by the black-tailed 

 Rorquals being those which feed on herrings and pilchards. 



