THE SEI WHALE 227 



the right side. Perhaps a smaller degree of asymmetry in the Sei whale is associated 

 with a less pronounced development of the habit of turning on to the side. 



The smallest foetus regarding which colour notes are available measured 1-3 m. in 

 length. In this the top of the head and snout were pigmented, except for large areas 

 round each eye. The outer surface of the left mandible was lightly, and the surface of 

 the flippers and the tip of the dorsal fin were fairly heavily, pigmented. The dorsal 

 surface, and the posterior margin of the ventral surface, of the flukes were pigmented. 

 The rest of the body was very pale. 



In the next largest foetus, measuring i -69 m. in length, the pigment was general over . 

 the dorsal surface of the body, with pigmented areas over each eye and an unpigmented 

 V-shaped area on the back with the apex at the level of the insertion of the flippers and 

 directed forward. The dorsal surface of the flippers and the margin of the ventral 

 surface of the flukes were pigmented. 



From this size onwards the adult pigmentation is reached by the extension and 

 darkening of the areas of pigment already present. The V-shaped light area on the 

 back is late in attaining its full coloration, so that it is more marked in the foetus than 

 in the adult. Between the lengths of 2 and 3 m. the under surface of the flippers 

 receives its pigmentation, if it is to be present, apparently on the right side first. 



The colour of the palate is pale pink or white with a small area of grey pigment at 

 the posterior end. The grey area usually fades gradually into the unpigmented anterior 

 part, but the line of demarcation is sometimes sharp. The grey area varies in size and 

 intensity of coloration and is sometimes much reduced centrally, so that it forms a small 

 median area with two streaks running forward on each side. In only one out of 

 seventy-six whales for which data relating to the palate were recorded was the posterior 

 grey patch on the palate absent. In addition to the posterior grey patch an anterior 

 grey patch of small extent was present in 6-5 per cent of the Sei whales and occurred 

 in both sexes. 



The tongue is dark slate-grey in colour, usually lighter on the under surface, but 

 occasionally darker. The colour is not always of even intensity all over the surface of 

 the tongue, but may vary so as to appear slightly blotched, or lighter at the margins. 



HAIR 



Hair occurs in the Sei whale on the upper surface of the head, on the ramus of the 

 jaws and on the chin. 



On the upper surface of the head the hairs occur in three series, a marginal line on 

 each side, a group on each side of the blow-hole, and a pair of lines, one on each side 

 of and close to the median line. The marginal lines are constant in their occurrence, 

 but the submedian lines or the blow-hole groups may be absent. The number of hairs 

 present on the upper surface of the head on one side varies from two to ten and 

 averages six. 



On the ramus of the jaws the hairs are arranged in one or two lines, which may be 

 rather irregular, and in one whale three lines of hair were noted. The arrangement of 



