On the Osteology of the HyopotamicUe. 175 



was indeed a welcome discovery — ancestor and descendant existing 

 together, the complete with the reduced form living about the 

 same period*. Moreover the didactyle form bore a great general 

 likeness in the structure of the limbs to Anoploiherium and Xi- 

 pJwdon, being perhaps only a Little more elaborate and better adapted 

 than these first experiments of the Eocene times. 



The likeness of the descendants allowed me to make inferences 

 as to the likeness of the ancestors ; and, taking into consideration 

 the structure of the limbs in the tetradactyle Hyopotamus, and the 

 rudimental second and fifth digit still existing in Anoploiherium, 

 Xiphodon, and Hyopotamus, I feel confident that the supposed an- 

 cestor of the first two did really possess a maims and pes very like 

 the projected typical diagram ; indeed we may be nearly as con- 

 fident of this as if we had found the actual thing imbedded com- 

 plete in some early Eocene or even Cretaceous rock. 



This, then, was the state of things in the earliest Eocene ; large 

 numbers of Paridigitata with tetradactyle feet like our Hyopo- 

 tamus, and the supposed progenitors of Anoploiherium and Xi- 

 pJwdon, represented the group of Paridigitates with crescentic teeth 

 (Selenodonta). Reduction in the number of digits, being an ad- 

 vantage to the organism, was steadily going on. But, be it ob- 

 served, we follow now the inadaptive line of descent ; and while 

 the whole weight of the body was, by gradual steps, entirely trans- 

 ferred to the two middle digits, these thickened and grew larger, 

 but entered into no special adaptation by means of which they 

 should better perform the work which had fallen to their share ; 

 they did not enlarge so as to gain additional support from all bones 

 of the second row of the carpus and tarsus ; the reduction was 

 inadaptive : inheritance is in them stronger than modification. 



Seeing that old Paridigitata present only two free metacarpals 

 and metatarsals, and that recent Buminantia have the same two 

 metacarpals and metatarsals coalesced into a single cannonbone, 

 evolutionists generally rush at the seemingly obvious conclusion 

 that once the tetradactyle foot reached the reduced state of two 

 digits, these coalesced together, and were transformed into the can- 

 nonbone of Bum in ants. No such thing, however, happened ; nor 

 could it have happened with the old didactyle Paridigitata, as the 

 Anoploiherium, Xiphodon, and Diplopus ; and the reason why it 

 could not is clearly indicated by the structure of their feet. We 

 have already shown that, following this inadaptive reduction, the 

 two middle digits, whilst growing larger, continue to occupy only 

 the inner half or more of the unciform and the greater part of the 

 os magnum ; so that from the outer as well as from the inner side 

 the carpal bones which support useless rudiments overhang the two 

 middle functional digits. In consequence of this, the distal surface 

 of the carpus was much broader than the proximal surface of the 

 two functional digits — an arrangement not calculated for firm equi- 



* Such cases are numerous. In the Sewalik Hills the Hipparion is associated 

 with the horse. 



