47 



The greatest circumference is between the pectorals and the dorsal fin, and amounts to barely half the length of 

 the bod}- (in the full-grown animal to more than half). 



The dorsal fin, which is shghtly convex in front and very concave at the back, is situated almost in the middle 

 of the body, though reaching a little over on to its anterior half, as in the female figured by Liitken (K. Danske Yid. 

 Selsk. Skr. 6 R. m. n. Afd. IV, 6, pi. I). The dorsal fin amounts to rather less than Via of the length of the trunk (in 

 the young female '/12. in the older female '/sj in the older male from -/s to Vs)- 



The breadth of the tail fin is equal to V4V, of the length of the trunk (in the younger animals from Vj to 'A, 

 and in the older ones from '/+ to '/■■!> according to Lilljeborg, 1. c.) 



These projjortions of the pectorals and other fins in relation to the length of the trunk confirm most fully the 

 general rule that all limbs and fins (caudal and dorsal fins) become longer with age (cf. Liitken, 1. c). 



The distribution of colour in this young one, agrees in all points with that commonly known in older specimens. 



Fig. 4. 



Outline of the tailfin ot' the 87.5 milhiu. long female fætiis of Orca gladiator, seen from ahove. 



The dark colour of the body is a deep blue-black, and the light colour beneath, cream-white (PI. V, fig. 2). There is no blue 

 or violet patch beside the dorsal fin. Passing over a few details at the junction of the black and the cream-white colours 

 between the pectorals and the angle of the mouth, it may be observed that the light colour is here found on the lower border of 

 the upper jaw, a circumstance which Lilljeborg states to be a rule, but which does not appear in the female figured by Liitken. 



General remarks. The generic and specific characters are perhaps developed earlier in the Orca than in many 

 other species of Odontoceti. It is remarkable that in a fætus that is hardly Vs of the length of the newly-born animal, the 

 generic characters are so distinct, that the fætus can without difficulty be distinguished from other Odontoceti. It is therefore 

 not surprising that Eschricht in his time, found that embryos of whales might be employed as an important aid in studying 

 the general form of the full-grown animal. "When the fn^iis has attained to half its full size (i. e. length), the specific 

 characters are distinctly visible, even in the distribution of colour, though of course there is still a want of distinctness in 

 tiic lines of demarcation and the more delicate shades of colour. There may possibly, too, be changes in this after birth. 

 But the various segments of the body are found with their ordinary conditions. In thus contemplating the newly-born animal, 

 one is involuntarily struck by the thought, that when Nature sows seed most sparingly for the maintenance of the species, 

 she comjiensates for it by making each seed perfect! We thus find that a newly-born Cetacean is one of the most fully 

 developed newly-bnrn animals in the whole class of Mammals. 



