THE SKELETON GF 
SKELETON OF THE LIMBS 
So far as their skeleton is concerned, the fore and hind limbs 
of Men and other Vertebrates, notwithstanding their various 
adaptive modifications, are unmistakably built on the same plan. 
This fact not only finds its expression in the strictly homologous 
segmentation of their free portions, but is confirmed by Compara- 
tive Anatomy and Ontogeny. 
Without entering at length into the old controversy as to 
the phylogeny of the limbs, I would briefly define my own posi- 
My. 
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Fic. 47.—TRANSVERSE SECTION THROUGH THE EMBRYO OF A SHARK (Pristiurus 
melanostomus), 9 mm. long, showing the mode of origin of the Pectoral Limb Bud (ap. ) 
ch., notochord ; co., ceelom ; m., myomeres, seen to be growing 
ventrally ; my., spinal cord. 
tion with regard to this question. I agree with Balfour and 
Dohrn in regarding the limbs of the Vertebrates as outgrowths 
of the primitive body segments, and thus believe in their originally 
segmental nature; and I see in this an argument for the origin 
of existing Vertebrates from segmented Invertebrate ancestors. 
In other words, these limbs, which in origin are polymerous, 
involve phylogenetically a certain number of body segments with 
their muscles and nerves; and these, in consequence of functional 
adaptation, must necessarily undergo different modifications in 
the different groups of Vertebrates. Although this subject 
cannot be further discussed here, it may be remarked, in passing, 
that the differences between the anterior and posterior limbs, 
resulting from adaptive modification, become less marked the 
lower we descend in the vertebrate series ; indeed, a starting-point 
