MORPHOLOGICAL METHOD AND RECENT PROGRESS IN ZOOLOGY. 587 



linporhiiit Ix'yond this, however, arc a series of Koeeiie forms which 

 more than till a loiio'-staiulinj;- ^ap, viz, that of the ancestors of the 

 elephants and niastodon.s, which hitherto stopped short in the Middle 

 Miocene of both Old and New Worlds. As represented by the genus 

 Mperttheriwii^ \h^Y have three incisors abo\-e and two below, of which 

 the second is in each case converted into a short but massive tusk. 

 An upper canine is present, and in both upper and lower jaws a series 

 of six cheek teeth, distinct and bunodont in type. In the allied Bary- 

 therium, of which a larg-o part of the skeleton is known, the upper 

 incisors were presumalily reduced to two, the tusks enlarg-ed, with 

 resemblances in detail to the Dinoceratan type. 



So far as these remains are known, they appear to present in their 

 combined characters all that the most ardent evolutionist could desire. 

 There are with them Mastodons, which simplify our knowledge of this 

 group, and among the last-discovered remains Sirenians, which, in 

 presenting a certain similarity to the afore-mentioned Mteritherium, 

 strengthen the belief in the pro))Oscidian relationships of these aquatic 

 forms. Finally, and perhaps most noticeable of all, there is the genus 

 ArsinoitlK'i'hiui^ a heavy brute with an olfactoi'v vacuity which out- 

 rivals that of Gi'ypotlicr'nnii itself, and is surmounted l)y a monstrous 

 fronto-nasal horn, swo11(mi and bitid, for which the most formidal)le 

 among the Titanotheres might yearn in vain. There is an occiput to 

 match! The suggestion that this extraordinary })east has relationships 

 with the llhinoceridie is absurd, since its tooth pattern alone inverts 

 the order of this type. Tliat it is prol)Oscidian may be nearer the 

 mark, and if so it show^s once more how su])tle were the mammals of 

 the past. Great as is this result much remains to be done or done 

 again, if only from the fact that in seeking to determine homologies 

 our American l)rethren, in the opinion of some of us, have placed too 

 much reliance on a so-called tritul>ercular theory of tooth genesis, of 

 which we can not admit the proof. How, we would ask, is it conceiv- 

 a])le that a transversely ridged molar of the T)i protodoii type can be 

 of tritubercular origin? 



Sufficient for the moment of paleontological advance, except to 

 remark that the zoologist who neglects this branch of mor})hology 

 miss(^s the one leavening influence; neghM'ts th(^ coui"t on whose ruling 

 arguments deduced from eml)rvological data alone must either stand 

 or fall. W(> may form our own conclusions from facts of the order 

 before^ us, but it is when we find their intiuence on the master mind 

 prompting to action, like that of Huxley with his mighty memoir of 

 1880, in which he revised our sulx-lass terms, that we a})pr(M'iate th(Mn 

 to the full. 



With this consideration w(> pass to the living forms, and 1 have oidy 

 time in dealing with these to conunent on advance which atfects our 

 broadest conceptions and classilications of the past. 



