504 THE SCIENTIFIC MONTHLY
with all that we are learning through paleontology and experimental evolution of the actual modes of the origin and development of adaptive characters. That there are elements of truth in each explanation is evident from the following. Adaptive characters present three phases : first, the origin of character-form and character-function; second, the more or less rapid acceleration or retardaton of character-form and function; third, the coordination and cooperation of character-forms and functions. If we adopt the physico-chemical theory of the origin and development of life it follows that the causes of such origin, velocity (acceleration or retardation) and cooperation must lie somewhere within the actions, reactions and interactions of the four physico- chemical complexes, namely, the physical environment, the developing organism, the chromatin, the living environment, because these are the only reservoirs of matter and energy we know of in life history. While it is possible that the relations of these causes will never be fathomed, it is certain that our search must proceed along the line of determining which actions, reactions and interactions invariably precede and which invariably follow, those of the body-cells (Lamarckian view) or those of the chromatin ( Darwinian- Weismann view).
The Lamarckian view that adaptation in the body cells invariably precedes similar adaptive reaction in the chromatin is supported neither by experiment nor by observation ; such precedence while occasional and even frequent is by no means invariable. The Darwinian view, namely, that chromatin evolution is a matter of fortuity and displays itself in a variety of directions, is contradicted by paleontological evidence both in the Invertebrata and Vertebrata, among which we observe that con- tinuity in chromatin evolution prevails over the evidence either of fortuity or of sudden leaps or mutations, that in many characters there is a prolonged rectigradation or direct evolution of the chromatin toward adaptive ends. This is what we mean in saying that in evolu- tion law prevails over chance.
Darwin's quest for the origin of species having become an incidental issue, the chief quest of evolutionists to-day is the origin and history of single characters. The discoveries of modern paleontology are in accord with many of the recently discovered laws of heredity, which will be described in the succeeding course of the Hale Lectures. Paleon- tology supports heredity in demonstrating that every vertebrate organ- ism is a mosaic of an inconceivably large number of "characters" or "character-complexes," structural and functional, some indissolubly and invariably grouped and cooperating, others singularly independent. For example, every one of the most minute scales of a reptile or hairs of a mammal is a "character complex" having particular chemical formulae and chemical energies which condition the shape, the color, and the function and all other features of the complex. Through re-
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