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body whose vertebrae are consolidated into a single 

 spinal piece. 



Or, this final vertebra may be resolved into a 

 series of vertebrae separating the fore-and rear- 

 limbs, in which case the ribs move on an artificial 

 ground furnished by the breast-bone. The trunk, 

 then, forming a compound spine, works on four 

 limbs, exterior to the whole, as in quadrupeds. 



Or, bringing the centre of motion more forward, 

 and more between the fore limbs, the animal may 

 be able to advance to some advantage with the 

 two rear limbs only as appuis on the ground. 



Or, finally, the centre of motion being brought 

 still further up, so that the neck, working between 

 the shoulders and the lower jaw, becomes the 

 master-centre of all motion, we have that highest 

 development of vertebrate structure into which 

 alone it has pleased God, as the consummation of 

 His plan for terrestrial creatures, in addition to in- 

 telhgence or even reason, to breathe a " living soul" 

 capable of knowing its Creator. 



"We think the epochs between these classes are 

 widely marked, and we are chiefly puzzled as to 

 where one may place the snake, which seems rather 

 to have come from stripping some animal of its 

 limbs than as a regular forward step ; for while the 



