WHALES 41 1 



The two sub-orders are thus on a par taxonomically, neither being a 

 derivative of the other. The mysticete eye is definitely less perfectly 

 adapted to aquatic use than that of the odontocete types; but this is not 

 because it is more primitive and has departed less far from the ancestral 

 terrestrial condition. Rather, one must think that the toothed ancestors 

 of the Mysticeti had better aquatic eyes than their descendants, perhaps 

 as well adjusted as those of modem odontocetes; and that in the Mysti- 

 ceti a certain degree of regression has occurred through a loss of impor- 

 tance of vision, correlated with the evolution of the trawling method of 

 feeding as opposed to the active visual predation of the squid- and fish- 

 eating Odontoceti. 



The mysticetes run to large size, the pygmy among them {Neoba- 

 Icena) being twenty feet long and the others — right whales, rorquals, the 

 humpback, and the archaic California gray — ranging from thirty-three 

 feet to over one hundred, the two sexes always being about equal. Their 

 cruising speed is slow, four to six knots; and some are incapable of swim- 

 ming more than about twice this fast. The great blue whale, largest of all, 

 is said to be able to swim out of sight in a few minutes; and the finner 

 (which feeds on herring as well as on krill) and Sei whales are capable 

 of great speed, the latter having been clocked at thirty knots. All baleen 

 whales have the habit of sounding, or frequently going to great depths, 

 rhythmically diving more shallowly and spouting betweentimes. All but 

 the very largest of them occasionally breach or leap clear of the water, 

 an action which is purely playful and not comparable with a jack-rabbit's 

 sky-hop. In fact, it is extremely doubtful if any whale ever puts so much 

 as its head out of water for the purpose of peering through air. The kill- 

 ers (Orcinus etc.) among the Odontoceti are credited with thus spying 

 out the ice floes for potential prey, and the cachalot has been claimed to 

 stand on its flukes and revolve slowly with the head out of water, sur- 

 veying the horizon. Identical actions on the part of various mysticetes, at 

 least, are clearly due to there being insufficient room between the floes 

 to bring the body up horizontally for spouting, necessitating an uprear- 

 ing of the head, which may even be rested on the ice for a time. 



Among the Odontoceti there is one type, the cachalot or sperm whale 

 (Physeter) , which imitates the baleen whales in many ways. It is by far 

 the largest of its group, the male (nearly twice the size of the female) 

 reaching sixty feet; and it is a slow swimmer — 3-4 knots, 10-12 when 

 pursued. The sperm whale moreover has the habit of sounding, and has 

 it even more conspicuously developed than does any mysticete. Physeter 



