716 ON FOKM AND MECHANICAL EFFICIENCY [ch. 



classificatory and phylogenetic aspect, which has all but filled 

 men's minds during the last couple of generations; and we can 

 lose sight of neither aspect without risk of error and misconception. 



It is certain that the question of phylogeny, always difficult, 

 becomes especially so in cases where a great change of physical 

 or mechanical conditions has come about, and where accordingly 

 the physical and physiological factors in connection with change 

 of form are bound to be large. To discuss these questions at 

 length would be to enter on a discussion of Lamarck's philosophy 

 of biology, and of many other things besides. But let us take 

 one single illustration. 



The affinities of the whales constitute, as will be readily 

 admitted, a very hard problem in phylogenetic classification. 

 We know now that the extinct Zeuglodons are related to the 

 old Creodont carnivores, and thereby (though distantly) to the 

 seals ; and it is supposed, but it is by no means so certain, that 

 in turn they are to be considered as representing, or as allied to, 

 the ancestors of the modern toothed whales*. The proof of any 

 such a contention becomes, to my mind, extraordinarily difiicult 

 and complicated ; and the arguments commonly used in such cases 

 may be said (in Bacon's phrase) to allure, rather than to extort 

 assent. Though the Zeuglodonts were aquatic animals, we do not 

 know, and we have no right to suppose or to assume, that they 

 swam after the fashion of a whale (any more than the seal does), 

 that they dived like a whale, and leaped like a whale. But the fact 

 that the whale does these things, and the way in which he does 

 them, is reflected in many parts of his skeleton — perhaps more 

 or less in all: so much so that the lines of stress which these 

 actions impose are the very plan and working-diagram of great 

 part of his structure. That the Zeuglodon has a scapula like that 

 of a whale is to my mind no necessary argument that he is akin 

 by blood-relationship to a whale : that his dorsal vertebrae are 

 very different from a whale's is no conclusive argument that 



* "There can be no doubt that Fraas is correct in regarding this type (Procetus) 

 as an annectant form between the Zeuglodonts and the Creodonta, but, although 

 the origin of the Zeuglodonts is thus made clear, it still seems to be by no means 

 so certain as that author believes, that they may not themselves be the ancestral 

 forms of the Odontoceti"; Andrews, Tertiary Vertebrata of the Fayum, 1906, 

 p. 235. 



