14 A BOOK OF WHALES 



dorsal fin in the Sperm whale may also be ascribable 

 to the retention of an embryonic condition.* In 

 Delphinapterus and JVeomeris, which are finless in 

 the adult condition, there is simply a low ridge in 

 the embryo. There is an ascending series in length 

 of the dorsal fin, when it is fully present, as in most 

 Delphinidae, which culminates in Orca, where the fin 

 is so large as to sometimes lie over at the top to one 

 side. So high and pointed is the dorsal fin of this 

 fierce Cetacean that it has been figured as a sharp 

 horn capable of sticking into the body of the whale- 

 bone whale, which this creature persecutes. The 

 function of the dorsal fin seems to be that of a 

 balancing organ ; and it is important to notice that 

 it is at its largest in the swift and carnivorous Orca. 



Dr. Murie is inclined to see in the dorsal fin a 

 representative of the hump or humps of the camels 

 and zebu. 



Such evidence as there is of the existence of two 

 dorsal fins consists in the first place of some observa- 

 tions made by MM. Quoy and Gaimard during the 

 voyage of the French ship Uranie. The testimony 

 of such observers must not be lightly rejected ; it 

 will be better to leave them to tell their own tale : 

 "In the month of October, 1819, going from the 

 Sandwich Islands to New South Wales we saw in 

 latitude 5.28 N. a number of dolphins performing 

 their rapid evolutions round the ship. Everybody 

 on board was surprised to see, as we did, on the 



* The dorsal fin of Ichthyosaurus was curiously like that of the Sperm 

 whale in this particular. 



