THE SEI WHALE 213 



It is of interest to note that in these figures there does not occur that pronounced 

 tendency for curves relating to the anterior part of the body to slope upwards from their 

 origin and those relating to the posterior part to slope downwards, as has been found 

 in other balaenopterid whales. In the curves for measurement No. 3, tip of snout to 

 blow-hole, Figs. 3 and 4, there is some slight tendency for the curves to take a general 

 upward slope from their origin, as there is also in those for measurement No. 6, tip 

 of snout to tip of flipper, Figs. 9 and 10. Conversely in the curves relating to females 

 only for measurements Nos. 10 and 12, notch of flukes to anus and to end of system 

 of ventral grooves respectively. Figs. 18 and 22, there is a general downward slope. 

 But on the whole there is a very marked absence of the general upward or downward 

 slope of the curves so characteristic of those based upon the measurements of other 

 species. The conclusion to be drawn is that in the Sei whale growth is much more 

 evenly distributed throughout the body and that marked differential growth in favour 

 of the anterior region does not occur to anything like the extent that it does in the 

 larger whales. 



The variations that occur in each measurement are shown in Table X, in which the 

 values of each measurement, expressed as percentages of the total length, are divided 

 into arbitrary groups and the number of values falling into each group are recorded. 

 These data are shown graphically in Figs. 43-61 in which the curves all approximate 

 closely to normal frequency curves, the least regular ones being those derived from 

 few data, or from measurements taken between ill-defined points and consequently 

 difficult to take uniformly. Only the data from whales taken at South Georgia are 

 included in these tables and figures: those from South African whales are omitted as 

 being too few in number. The curves relating to data from females are the most accurate 

 because they are constructed from nearly three times as many measurements as those 

 relating to males. The range of variation in the measurements shown in these figures 

 indicates a homogeneous population, and no admixture of races with structural 

 differences. 



COLOUR 



Colour notes were made on ninety-six Sei whales, twenty-four males and seventy-two 

 females. No colour differences between the sexes were observed. 



The coloration of the Sei whale shows considerable variation. Dorsally the colour 

 is some shade of grey, usually rather lighter than in the Fin whale, but in 11-5 per cent 

 of the whales examined it was conspicuously darker. Ventrally the colour is light. On 

 the ventral grooves there is always a white area of greater or lesser extent. This white 

 area runs from the chin backwards, and when fully developed covers the whole of the 

 ventral grooves but does not extend on to the mandible. More usually, however, it 

 stops short of the posterior end of the grooves, but only rarely is its posterior margin 

 sharply defined ; more commonly it fades gradually into the posterior ventral coloration 

 to be described below. The white area may fail to reach the posterior end of the ventral 

 grooves by a distance of 1-3 m. (PI. XVIII, figs, i and 2), while one instance occurred 

 in which it extended only for a distance of 1-5 m. from the chin, forming a large white 



