GENERAL CONCLUSIONS. 795 



derivative law exemplified in the series linking on Palceotherium 

 to Equus? A very significant one is the following : — A modern 

 horse occasionally comes into the world with the supplementary 

 ancestral hoofs. From Valerius Maximus, 1 who attributes the 

 variety to Bucephalus, downwards, such ' polydactyle ' horses 

 have been noted as monsters and marvels. In one of the latest 

 examples, 2 the inner splint-bone, answering to the second me- 

 tacarpal of the pentadactyle foot, supported phalanges and a 

 terminal hoof, in position and proportion to the middle hoof, re- 

 sembling the corresponding one in Hipparion, fig. 614, n. 



In relation to actual horses such specimens figure as ' monstra 

 per excessum;' 3 but, in relation to miocene horses, they would be 

 normal, and those of the present day would exemplify 'monstra per 

 defectum.' The mother of a ( monstrous' tridactyle colt might repeat 

 the anomaly and bring forth a tridactyle e filly '; just as, at San 

 Salvador, the parents of a family of six had two of the series born 

 with defective brain and of dwarf size : they were ( male ' and 

 'female ;' and these strange little idiots are exhibited as 'Aztecs.' 

 The pairing of the horses with the metapodials bearing, accord- 

 ing to type, phalanges and hoofs, might restore the race of 

 hipparions. 



Now, the fact suggesting such possibility teaches that the 

 change would be sudden and considerable : it opposes the idea 

 that species are transmuted by minute and slow degrees. It also 

 shows that a species might originate independently of the opera- 

 tion of any external influence; that change of structure would 

 precede that of use and habit ; that appetency, impulse, ambient 

 medium, fortuitous fitness of surrounding circumstances, or a 

 personified ' selecting Nature,' would have had no share in the 

 transmutative act. 



There is, however, one relation which I cannot shut out, 

 for I hold it as strongly as when I explained it, and endeavoured 

 to impress it upon the audience at my lectures of 1857 : it is the 

 fitness of the organisation of the Horse and Ass for the needs of 



1 ' Exemplorum memorabilium Libri novem, &c. (De rebus mirifieis.) ' 



* cccrv". p. 55, PI. 1. 



* Two such examples are described in mi. vol. ii., and one in cccv". p. 224, in which 

 the left fore-foot had three subequal hoofs, and the right fore-foot two hoofs. But the 

 application of an instructive and rightly discerned relation may be travestied and exag- 

 gerated : the two-tailed lizard and the double-headed snake do not reproduce to view 

 normal ancestral forms. The essentially single mid-toe (fig. 193, iii) of the horse, oc- 

 casionally bifid and terminated by a pair of ill-shapen hoofs, lends no support to the 

 idea of the digit (iii) being homologous with the so-called cloven hoof (really the digits 

 iii and iv, ib.) of Ruminants. It is a malformation akin to that of the partially 

 double digit of the Dorking fowl. 



