Xii.] THE ORIGIN OF SPECIES. 259 



associated characters. They have 1. A vertebral column ; 

 2. Mamma) ; 3. A placental embryo ; 4. Four legs ; 5. A 

 single well-developed toe in each foot provided with a 

 hoof ; 6. A bushy tail ; and 7. Callosities on the inner 

 sides of both the fore and the hind legs. The asses, 

 again, form a distinct species, because, with the same 

 characters, as far as the fifth in the above list, all asses 

 have tufted tails, and have callosities only on the inner 

 side of the fore leffis. If animals were discovered ha vine: 

 the general characters of the horse, but sometimes with 

 callosities only on the fore legs, and more or less tufted 

 tails ; or animals having the general characters of the 

 ass, but with more or less bushy tails, and sometimes 

 with callosities on both pairs of legs, besides being inter- 

 mediate in other respects — the two species would have 

 to be merged into one. They could no longer be 

 regarded as morphologically distinct species, for they 

 would not be distinctly definable one from the other. 



However bare and simple this definition of species 

 may appear to be, we confidently appeal to all practical 

 naturalists, whether zoologists, botanists, or palaeonto- 

 logists, to say if, in the vast majority of cases, they 

 know, or mean to affirm, anything more of the group of 

 animals or plants they so denominate than what has just- 

 been stated. Even the most decided advocates of the 

 received doctrines respecting species admit this. 



u I apprehend," says Professor Owen, 1 "that few naturalists now- 

 a-days, in describing and proposing a name for what they call ' a new 

 species' use that term to signify what was meant by it twenty or thirty 

 years ago ; that is, an originally distinct creation, maintaining its 

 primitive distinction by obstructive generative peculiarities. The pro- 

 poser of the new species now intends to state no more than he 

 actually knows ; as, for example, that the differences on "which he 



1 On the Osteology of the Chimpanzees and Orangs : Transactions of the 

 Zoological Society, lb58. 



