180 Prof. C. O. Whitman,


Dove {Geopelia cuneata), of Australia. In passing from the

juvenal color-pattern to that of the adult, we seem to pass to a

pattern that is wholly new, and without transitional phases. It

looks like an unpremeditated jump, such as we should expect in

biogenetic recapitulation, if mutation were the law of the origin

of species. In the adult bird we have a grey ground with the

coverts of the wing very regularly marked each with two white

dots, one on each side of the feather, equidistant from the apex.

In the young bird we have no white dots, but some irregular

cross-lines (' bars') of a light color. How can we pass without a

jump from one pattern to the other?


A very simple experiment will show how this may be

done. All we have to do is to pull out a few of the juvenal

feathers at suitable intervals of time. Their places will soon be

filled by new feathers of different ages, and these will give inter-

mediate stages in the transformation of the cross-lines of the

young into the white dots of the adult. The adult pattern is

thus revealed as an end-stage of a continuous process of differ-

entiation. The same experiment may be made in other species

with similar results.


The pigeons, wild and domestic, present a considerable

number of specific characters, the histories of which can be

traced with exceptional fullness, sometimes in great detail. In the

wing-bars, for example, where we have, not oiie such character

merely, but many, it is possible to read the several histories with

much greater fullness and certainty than would be the case if

they occurred only in single species.


In the genesis of these bars it is possible to see that

natural selection has not been the primary factor, and that mu-

tation, as defined by De Vries, has not been required either as

primary or secondary factor. It is only on Darwin's hypothesis,

that bars came first and chequers afterwards, that mutation

would find a locus sta?idi. But origin de novo is an entirely inad-

missible hypothesis, when we can trace the history of the bars

back to remote ancestral foundations.


The mutationist is compelled to take his stand on immut-

able unit-characters. A character may fluctuate to and fro, but

it never loses its balance, except by a sudden transformation that



