Mammals to Aquatic Life. 155 



directions. Tims we are at once able to assign the water-rat 

 to the voles (ArvicolidEe), the otter to tlie martens ; but of the 

 seals we are only able to say in a general way that they are 

 allied to the Carnivores, as the Sirenians are to the Ungulates ; 

 while of the relationships of the typical aquatic mammals, 

 the whales, we at present know nothing. Not that no 

 hypotheses have been set up to explain the origin of the 

 whales ! The question of their descent has been largely 

 ventilated, and the majority of the zoologists who have attacked 

 the problem have not been behindhand with their answer. 

 Let us pass over for the nonce the views of the older authors, 

 and devote ourselves to the most modern theories of the pliylo- 

 geny of the Cetacea ! 



Some naturalists consider the whales to have sprung directly 

 from the hypothetical Pro-Mammalia, and to be therefore 

 closely allied to the Reptiles, basing their hypothesis on simi- 

 larities in structure, particularly with certain extinct reptiles, 

 the Ichthyosauri ; others place them near the Ungulates, with 

 which they are supposed to be connected through the Sirenians. 

 By other authors, again, the whales are held to be allied to the 

 seals or to the Caruivora in general ; nay, they are even said 

 to lead to the seals through the Sirenians ; and of the most 

 recent workers at the group, one (Weber) comes to the con- 

 clusion that the whales possess certain cliaracters pointing 

 to affinities with the Carnivora, particularly with the seals, 

 and others which suggest a relationship to the Ungulates ; 

 while the other investigator (Leboucq) is convinced, from the 

 results of his work on the flipper, that in the whales we have 

 extremely ancient mammals, whose ancestors never lived on 

 land, but were only swamp-dwellers. 



This is briefly what the most modern theories of the phylo- 

 geny of the whales amount to, and the views expressed are so 

 divergent as not to convey an exalted idea of the present 

 position of phylogenetic science. The thought involuntarily 

 strikes us whether the method of phylogenetic inquiry may 

 not in this case be somewhat inefficient. If we follow in 

 detail the path which the various investigators, among them 

 the foremost zoologists of the age, have each one pursued, we 

 find that, of the various methods of obtaining phylogenetic 

 knowledge, it has always been that of comparative anatomy 

 which they have adopted, and that it has ever been similarities 

 in structure with another group of animals which have per- 

 suaded them, according as they attached greater or less 

 importance thereto, toconnect the whales with thelchthyosaurs, 

 the Seals, or the Carnivores, with the Sirenians or tlie Ungu- 

 lates. 



11* 



