130 REV. JOHN GERARD, F.L.S., ON SPECIES AND THEIR ORIGIN. 
organic and inorganic, should recur.” From this it must follow 
that every species now existing is made up of descendants of one 
single ancestral pair, other descendants from the more distant 
common ancestor having disappeared. But, to take the simplest 
of Mr. Wallace’s examples, the forms intervening between 
thrushes and crows and their original common ancestor must have 
been immensely numerous along each line of descent, and of 
these intervening forms each must have belonged to some 
species, which for the time being had succeeded in establishing 
or continuing itself, though it had finally to yield its place in 
favour of other representatives of the same kindred, which had 
better adapted themselves to the conditions of life. According 
to this, each evolutionary stage which was marked by the 
appearance of a group so distinctive as to be styled a new 
species, must have witnessed the extinction of a multitude of 
near relatives which had not  sutticiently accommodated 
themselves to actual conditions, an extinction which took the 
form, not, as was once supposed, of a catastrophe or general 
massacre, like that of royal princes on the accession of a new 
sultan, but of a gradual dropping off of those less fitted to 
survive. But, at any rate, this seems to be clear, from what 
Mr. Darwin tells us, that in every instance a species has started 
from progenitors which had developed characters distinguishing 
them specifically from others descended from the same ancestry, 
and which, because of such distinguishing characters, became the 
sole survivors of their race. 
Many points are here suggested which seem worthy of more 
attention than they have usually received, but at present we 
may concern ourselves with one only, which brings us back to 
that from which we may seem to have digressed. Can 
community of descent furnish a satisfactory basis for the 
classification of species, if it constantly happens, and as it were 
inevitably, that amongst the descendants of the same progenitors 
specific differences are produced? As Professor Bowne says :— 
“Descent, as such, carries nothing with it in the intellectual 
system. It is merely the actual method by which the organic 
system has been realised, but 1t becomes such a method only 
because it is so adjusted as to produce the result. The 
systematic relations of things in a graduated and ordinated 
scale of existence were insisted upon long before the doctrine 
of descent was thought of, and this doctrine adds nothing to 
that earlier view, except a conception of the way in which that 
intellectual order was realised. But, as just said, descent alone 
explains nothing unless its inner order presupposes just this 
