16 



Professor Flower 



[May 25, 



hind-limbs into instruments of propulsion through the water; for 

 though the thighs and legs are small, the feet are large and 

 are the special organs of locomotion, the tail being quite rudi- 

 mentary. The two feet applied together form an organ very like the 

 tail of a fish or whale, and functionally representing it, but only 

 functionally, for the time has I trust quite gone by when the Cetacea 

 were defined as animals with the " hinder limbs united, forming a 

 forked horizontal tail." In the whales, as we have seen, the hind- 

 limbs are aborted and the tail developed into a powerful swimming 

 organ. Now it is very difficult to suppose that when the hind-limbs 

 had once become so well adapted to a function so essential to the 

 welfare of the animal as that of swimming, they could ever have 

 become reduced and their action transferred to the tail ; — the animal 

 must have been in a too helpless condition to maintain its existence 

 during the transference, if it took place, as we must believe, gradually. 

 It is far more reasonable to suppose that whales were derived from 

 animals with large tails, which were used in swimming, eventually 

 with such effect that the hind-limbs became no longer necessary, and 

 so gradually disappeared. The powerful tail, with lateral cutaneous 

 flanges, of an American species of otter (Pteronura sandbachii) or the 

 still more familiar tail of the beaver, may give some idea of this 

 member in the primitive Cetacea, I think that this consideration 

 disposes of the principal argument in favour of the whales being related 

 to the seals, as most of the other resemblances, such as those in the 

 characters of their teeth, are evidently resemblances of analogy related 

 to similarity of habit. 



As pointed out long ago by Hunter, there are numerous points in 

 the structure of the visceral organ of the Cetacea far more resembling 

 those of the Ungulata than the Carnivora. These are the complex 

 stomach, simple liver, respiratory organs, and especially the repro- 

 ductive organs and structures relating to the development of the 

 young. Even the skull of Zeuglodon, which has been cited as pre- 

 senting a great resemblance to that of a seal, has quite as much likeness 

 to one of the primitive pig-like Ungulates, except in the purely 

 adaptive character of the form of the teeth. 



Though there is, perhaps, generally more error than truth in 

 popular ideas on natural history, I cannot help thinking that some 

 insight has been shown in the common names attached to one of the 

 most familiar of Cetaceans by those whose opportunities of knowing 

 its nature have been greatest — " Sea-Hog," '* Sea-Pig," or " Herring- 

 Hog " of our fishermen, Meerschwein of the Germans, corrupted into 

 the French "Marsouin," and also " Porcpoisson," shortened into 

 " Porpoise." 



The difficulty that might be suggested in the derivation of the 

 Cetacea from the Ungulata, arising from the latter being at the 

 present day mainly vegetable feeders, is not great, as the primitive 

 Ungulates were probably omnivorous, as their least modified descend- 

 ants, the pigs, are still ; and the aquatic branch might easily have 



