iting, that not only is it an iapostibiliiy to lay down 
this precise definition of species * between two or more 
skeleton forms of animals, but it is impossible eyen to 
define a constant and fixed special variety between two or 
more osseous quantities of the one skeleton serial axis ; nay, 
it is a positive fact that the isolated thing, fig. B, or C, or 
A”, is not always produced in the condition such as we see it 
here, for do we not find that either of these figures passes 
through the variations of excess and defect? To what 
~ end, therefore, let us ask, is this laboured search after the | 
limit of special variety and the differential method to lead? 
Is this finis page of the subject of SpeGHe distinctiveness 
* a ae: . 5 € ee 
“ >. * - «* ™ 
1% : oe ON THE FIGURES OF PLATE XVII. reed Pag 
* : — f 
to be found somewhere amongst the infinity of osteological 
and Paleontological facts of. development ? Is it still 
buried amongst some unknown mass of facts which are 
one day to be discovered 4, us, or does it lie concealed in 
some as yet undiscovered law, which awell-grounded prin- — 
ciple of comparison carried. out upon the facts already 
known might eye to us? Before we pass’ into the 
subject of animal species, let us first understand somethings 
of how fig. A”, the asternal-costo-vertebral forms, are 
different to fig. A’, the sterno-costo-vertebral eee 
of series. 
RO ONING epaehal this whole mystery of genera and species, Sing make such a noise in the schools, and are with justice so little regarded 
out of them, is nothing else but abstract ideas, more or less comprehensive, with names annexed to them. 
In all which this is constant and 
invariable, that every more general term stands for such an idea, and is but a part of any of those contained under it.”—Locke—General Terms 
Human Understanding, vol. i., p. 439, 20th edition. 
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