Differences Of Opinion As To The Factors In Evolution

The theory of natural selection in the struggle for existence rapidly

gained wide acceptance, but from the first it was called in question from

many sides. Bronn, who translated Darwin's works into German, was and

remained loyal to the idea of a "developmental law"--that there is within

the organism an innate tendency towards self-differentiation and progress,

thus a purely teleological principle.(34) Similarly, von Baer emphasised br />
the idea of an endeavour to realise an aim; von Koelliker, that of

"heterogenesis"; Naegeli, that of an impulse towards perfection--all three

thus recognising the theory of evolution, but dissenting from the view

that the struggle for existence is the impelling factor and actual guide

in the process. Very soon, in another direction, antagonism became

pronounced between the strictly Darwinian elements of the theory (the

struggle for existence and its corollaries) and the accessory Lamarckian

elements. Through these and other controversies the present state of the

question has emerged.



The main antithesis at present is the following. On the one side, the

"all-sufficiency of natural selection" is maintained, that is, progressive

evolution is regarded as coming about without direct self-exertion on the

part of the organisms themselves, simply through the fact that fortuitous

variations are continually presenting themselves, and are being selected

and established according to their utility in the struggle for existence.

On the other side--with Lamarck--the progress is regarded as due to effort

and function on the part of the organism itself. (Increased use of an

organ strengthens it; a changed use transforms it; disuse causes it to

degenerate. Thus new characters appear, old ones pass away, and in the

course of thousands of years the manifold diversity of the forms of life

has been brought about.)



Further, by those of the one side variation is regarded as occurring by

the smallest steps that could have selective value in the struggle for

existence. To the others variation seems to have taken place by leaps and

bounds, with relatively sudden transformations of the functional and

structural equilibrium on a large scale. In regard to these the role of

the struggle for existence must be merely subsidiary. This saltatory kind

of evolution-process is called "halmatogenesis," or, more neatly,

"kaleidoscopic variation," because, as the pictures in a kaleidoscope

change not gradually but by a sudden leap to an essentially new pattern,

so also do the forms of life. Associated with this is the following

contrast. One side believes in free and independent variation of any

organ, any part, any function, physical or mental, any instinct, and so

on, apart from change or persistence in the rest of the organism; the

other side believes in the close connectedness of every part with the

whole, in the strict "correlation" of all parts, in variation in one part

being always simultaneously associated with variation in many other parts,

all being comprised in the "whole," which is above and before all the

parts and determines them. And further, to one school variation seems

without plan in all directions, simply plus or minus on either side of a

mean; to the other, variation seems predetermined and in a definite

direction--an "orthogenesis," in fact, which is inherent in the organism,

and which is indifferent to utility or disadvantage, or natural selection,

or anything else, but simply follows its prescribed path in obedience to

innate law. The representatives of this last position differ again among

themselves. Some regard it as true in detail, in regard, for instance, to

the markings of a butterfly's wing, the striping of a caterpillar, the

development of spots on a lizard; while others regard it as governing the

general process of evolution as a whole. Finally, there is the most

important contrast of all. On the one side, subordination, passivity,

complete dependence on the selective or directive factors in evolution,

which alone have any power; on the other, activity, spontaneous power of

adaptation and transformation, the relative freedom of all things living,

and--the deepest answer to the question of the controlling force in

evolution--the secret of life. This last contrast goes deeper even than

the one we have already noted, that between the Darwinian and the

Lamarckian principle of explanation; and it leads ultimately from the

special Darwinian problem to quite a new one, to be solved by itself--the

problem of the nature and secret of living matter.