animals themselves ? They appear capable of interpretation only as
the preparation for a vertebral column and a spinal cord to be after
wards evolved. . . . But the strongest instance of the kind
which I know of, except that of the brain of man, is the existence
of pneumatic bones (that is to say, bones hollowed out for lightness,
like those of flying birds) among Dinosaurians (see Professor Cope’s
paper on Mcgadactylus probyzelus, as reported in Nature, vol. i.,
p. 347). The resemblances of the skeleton appear to prove that
birds must be descended from Dinosaurians. No Dinosaurian had
the power of flight, yet here is a character useful only to flying
animals, and interpretable only as a preparation for a power of flight
to be afterwards evolved.”—(Nature. vol. xxxviii., pp. 411-12.)
In order to show that Natural Selection has had no part
in the evolution of a nascent organ, it would be necessary
to prove that at no transitional stage of the development
has the organ been of any use to the animal in which it is
developed. Have we any such instance of a tendency to
develope in definite lines, so that when the evolution is
complete, and only then, it is capable of performing a
useful function ? Of course it would be natural for the
theologian to interpret such a phenomenon as an indication
of “purpose” ; and looking at the matter from this point
of view, Mr. Romanes speaks in no uncertain manner:—
“To deal with the important question before us (the highly-
specialised and long-elaborated structures) therefore, we must fasten
attention exclusively upon incipient variations, or variations as they
occur de novo in first generations. Now I request any teleologist to
produce evidence that such incipient variations ever exhibit any
particular tendency to occur in definite lines—still less in lines
suggestive of any ultimate ‘ purpose.’ And I make this request
because it clearly rests with the teleologist to furnish some such
justification of his belief, that the causative influence of Natural
Selection is supplemented (either wholly or partly) by some causative
influence of another and ulterior kind, which is supposed to furnish
variations only in definite, not to say ‘prophetic’ lines. Yet I make
this request, well knowing that it cannot be complied with. For,
notwithstanding the opinions expressed by Asa Gray, Nageli, and
the others, no one has hitherto been able to point to any instance
of incipient variations thus tending to occur only in definite lines ;
while, on the other hand, the success of breeders and horticulturalists
furnishes overwhelming proof that variations occur in such a number