BRIEF SKETCH OF THE TOOTMED WHALES. 101 



and the latter group {viz. the Seals and Walruses). Prof. Ryder, 

 of the University of Pennsylvania, agrees with him, and, 

 further, believes that the terminal parts of the posterior limbs 

 are represented externally by the flukes. Prof. Albrecht links 

 them with his hypothetical Promammalia. Sir William Flower, 

 again, who thinks the Whales were derived from terrestrial 

 mammals with four limbs, with a hairy covering, with sense- 

 organs — especially smell — adapted for living on land, strongly 

 objects to the views just mentioned, since the Seal has been 

 adapted for its aquatic life by the peculiar development of its 

 hind limbs, while the tail is rudimentary. The greatly de- 

 veloped hind feet functionally represent the tail of the Cetaceans 

 in which the hind limbs are absent. He thinks it difficult to 

 suppose that when the hind limbs had once been so well adapted 

 for swimming they could ever have been reduced and their 

 action transferred to the tail. The animal must have been in 

 too helpless a condition to maintain its existence during the 

 transference. He considers it more reasonable to suppose that 

 the Whales were derived from animals with large tails, which 

 were used in swimming, and eventually with such effect that the 

 hind limbs became no longer necessary. He instances such 

 tails, for example, as in the American Sea-Otter {Pteroneura 

 sandbachii) , or the Beaver. 



These theories, however, leave the inquirer very much where 

 they found him, and there is still a want of anything approach- 

 ing a complete ancestry of the remarkable animals which have 

 formed the subject of these remarks. The absence of such 

 explanations, however, detracts little from the interest asso- 

 ciated with the striking modifications of mammalian structure, 

 the social and other instincts, the economic value, and the 

 peculiar habits which make them traverse the seas from the icy 

 Polar regions to temperate latitudes on the one hand, and on the 

 other pass up fresh-water rivers for more than a thousand miles. 

 Their whole organization marvellously adapts them for their 

 special existence, and it can only be a cause for regret that their 

 persevering pursuit by man, aided by every modern invention, 

 is in many cases rapidly thinning the ranks of animals so full 

 of scientific as well as general interest. 



Finally, few, even among zoologists, have devoted attention 



