Paleontology. 199 
wise furnish characters which further serve to establish 
this dual relationship 1.” 
The evidence, then, which is furnished by all parts 
of the vertebral skeleton—whether we have regard to 
Fishes, Reptiles, Birds, or Mammals—is cumulative 
and consistent. Nowhere do we meet with any de- 
viation or ambiguity, while everywhere we encounter 
similar proofs of continuous transformation—proofs 
which vary only with the varying amount of material 
which happens to be at our disposal, being most 
numerous and detailed in those cases where the 
greatest number of fossil forms has been presérved 
by the geological record. Here, therefore, we may 
leave the vertebral skeleton; and, having presented 
a sample of the evidence as yielded by horns and 
bones, I will conclude by glancing with similar brevity 
at the case of shells—which, as before remarked, con- 
stitute the only other sufficiently hard or permanent 
material to yield unbroken evidence touching the 
fossil ancestry of animals. 
Of course it will be understood that I am everywhere 
giving merely samples of the now superabundant 
evidence which is yielded by paleontology ; and, as 
this chapter is already a long one, I must content 
myself with citing only the case of moilusk-shells, 
although shells of other classes might be made to 
yield highly important additions to the testimony. 
Moreover, even as regards the one division of mollusk- 
shells, I can afford to quote only a very few cases. 
These, however, are in my opinion the strongest 
single pieces of evidence in favour of transmutation 
which have thus far been brought to light. 
1 Heilprin, Geological Evidences of Evolution, pp. 73-4 (1888). 
