IMPORTANCE OF THE SKELETON. 277 



variety of forms indeed, but yet in the same characteristic 

 arrangement and relative position ; and if the comparison 

 of the anatomical conditions of the skeleton is carried out 

 below Mammals, we can prove that a direct and uninter- 

 rupted connection exists throughout between these various 

 forms which are apparently so utterly unlike, and can 

 finally be traced from a most simple, common, fundamental 

 form. These facts alone must fully convince every ad- 

 herent of the Theory of Development that all Vertebrates, 

 including Man, must be traced from a single common 

 parent-form, from a Primitive Vertebrate; for the mor- 

 phological features of the inner skeleton, and of the mus- 

 cular system which stands in the closest correlative rela- 

 tions to it, are of such a kind that it is quite impossible 

 to conceive a polyphyletic origin, a descent from several 

 different root-forms. It is impossible, on mature reflection, 

 to accept the theory that the vertebral column with its 

 various appendages, or the skeleton of the limbs with their 

 variously differentiated parts, could have originated on 

 several occasions during the course of the earth's history, 

 and that, consequently, the various Vertebrates must be 

 referred in various lines of descent from Invertebrates. 

 Indeed, it is exactly in this point that Comparative Anatomy 

 and Ontogeny irresistibly drive us to the monophyletic 

 conclusion, that the human race is a very recent offshoot 

 of the same great single trunk, from branches of which all 

 other Vertebrates have also sprung. 



In order to obtain a view of the outlines of the develop- 

 ment of the human skeleton, we must first take a general 

 survey of its arrangement in the developed Maa (Of. 

 Table XXXIV. and Fig. 251, the human skeleton from the 



