EVIDENCE FROM TAILS, LIMBS, & LUNGS OF ANIMALS, in 



A primary remark, of some importance in investigations like the 

 present, would insist on our recognising that a series of deep-seated 

 likenesses in internal structure, such as that presented to our notice 

 in the limbs, is much more likely to be truly accounted for by some 

 natural law of development than by any mere chance production, or 

 by any spontaneous resemblance existing apart from natural affinity. 

 If we assume for a moment the position of a holder of the " special 

 creation " theory, we may form some idea of the difficulties which 

 beset the reasonable imagination in accounting for likenesses of such 

 well-marked character as the limbs of vertebrates exhibit. In each 

 case we should require to postulate a new and special creative act 

 which had, according to no known or conceivable law, modelled 

 these appendages on one and the same type a system of creation 

 given to the preservation of useless rudiments of once useful 

 structures, instead of simply giving to each animal the exact organs 

 and parts it requires. True, such a method of creation may be 

 conceivable, but nothing more, if we reflect once again upon the 

 extraordinary likeness and on the evident common relationship of the 

 limbs. But this creative theory entirely loses caste and status when 

 placed in contrast with the more reasonable theory of descent. By 

 means of this latter explanation we account for limb-likeness on the 

 principle of natural inheritance, and on the relationship, through 

 descent, of the animals which bear the related limbs. We thus see in 

 limb-likeness merely the natural result of descent from a common 

 ancestor or ancestors, in which the .fundamental limb-type was 

 developed. The law of likeness, whereby the offspring tend to 

 resemble the parent, in fact demands common limb-likeness as the 

 natural heritage of all vertebrate animals, and presents the theory ot 

 descent as the only natural solution of the query, "< Why are limbs 

 modelled on one and the same type?" 



As Darwin himself remarks, 

 "what can be more curious than 

 that the hand of a man formed 

 for grasping, that of a mole for 

 digging, the leg of the horse, the 

 paddle of the porpoise, and the 

 wing of the bat, should all be 

 constructed on the same pattern, 

 and should include similar bones 

 in the same relative positions? 

 How curious it is, to give a sub- 

 ordinate though striking instance, 

 that the hind feet of the kangaroo 

 (Fig. 49, A), which are so well fitted 



FIG. 49. FEET OF MARSUPIALS. 



for bounding over the open 



plains those of the climbing leaf-eating koala, equally well fitted 



