162 The Mendel Journal
assault. The right and left are in possession of the Mendelians, the centre has been reconnoitred and the attack is beginning. But it is here that the conflict must be necessarily prolonged, on account of the difficult nature of the country to be conquered. For it is here that the great challenge must be made and accepted, as to whether evolution is wholly a matter of that organic advance which would result from the blending in successive generations of minute, barely perceptible variations, existing simultaneously in large masses of individuals; or whether it is wholly a matter of more or less irregular advance, sometimes small, sometimes great, due to the spontaneous appearance in a single individual of a mutational character or "sport," and which in its inheritance, through succeeding generations, segregates cleanly and definitely, from its opposite or allelomorphic factor, already present in the race; or whether evolution is partly due to the one and partly to the other. The existence of selection and elimination, without which there could be no evolution, by either method, is defended by both armies.
The battle of the future which is to be fought between these two armies therefore turns upon the nature of "Intermediates." And it is along this range of biological hills that the Biometrical centre is concentrating. Do these intermediate stages between the two extremes of a character necessarily manifest the existence of gametic blending, or do they represent simply a series of segregable grades? That there do exist phenomena which at a first examination and in the absence of any extended experimental knowledge would justify us in the belief that they indicate the existence of blended characters is not denied. But the Mendelians assert that the appearances are false, that they need re-investigation by experimental methods, and that our present knowledge renders it easy for us to conceive of the existence of segregation without there being any obvious manifestation of its existence. The Biometricians impliedly maintain that the existence of a character is inconsistent with the segregation of those two extremes, and also with the segregation of the intermediates themselves. And,
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