THE PROBLEMS PRESENTED. In his classical work on Heredity, Professor J. Arthur Thomson exhausts the evidence on Lamarckism available then (1908) in a manner worthy of the summing-up of an English judge. This is presented to the jury of the biological world and they are still considering it. Their verdict and his sentence are not yet delivered, and it may be they will still be long delayed. One might almost use the words of Professor Bateson, previously quoted, “on our present knowledge the matter is talked out.” I will make one prophecy in this volume and predict that the fourth edition of this work in 1930 will contain the verdict of the jury and sentence of the distinguished judge to the effect that in the case Lamarck _v._ Weismann the plaintiff has won. As in the Great War the Old Contemptibles held their line with the utmost difficulty against the disciplined hosts of the greatest army ever known till then, and yet the latter found their First Battle of the Marne, so perchance it may be in the present struggle. I introduce this chapter with an important passage from the above work on the _Logical position of the Argument_, in which the two possible methods of establishing the affirmative position of Lamarck are given; these are, first, actual experimental proof of transmission, and, second, a collection of facts which cannot be interpreted without the hypothesis of modification inheritance. The words are:[28] “_The neo-Lamarckians have to show that the phenomena they adduce as illustrations of modification-inheritance cannot be interpreted as the results of selection operating on germinal variations. In order to do this to the satisfaction of the other side, the neo-Lamarckians must prove that the characters in question are outside the scope of natural selection, that they are non-utilitarian and not correlated with any useful characters--a manifestly difficult task. The neo-Darwinians, on the other hand, have to prove that the phenomena in question cannot be the results of modification-inheritance. And this is in most cases impossible._”[29] [28] _Heredity_, 1908, p. 240. [29] I prefer to state the above passage rather than that on page 179, which is as follows: “The precise question is this: _Can a structural change in the body, induced by some change in use or disuse, or by a change in surrounding influence, affect the germ-cells in such a specific or representative way that the offspring will through its inheritance exhibit, even in a slight degree, the modification which the parent acquired?_” (Italics in original). The question is very precise and important, but I employ that given above in preference as lending itself better to the line of inquiry followed here.