Among the vitalists of to-day, one of the most frequently cited, perhaps, except Driesch the most frequently cited, is G. Wolff, a _Privatdozent_, formerly at Würzburg, now at Basle. He has only published short lectures and essays, and these deal not so much with the mechanical theory as with Darwinism.(86) But in these writings his main argument is that of his concluding chapter: the spontaneous adaptiveness of the organism, which nullifies all contingent theories to explain the purposiveness in ontogeny and phylogeny. And in his lecture, “Mechanismus und Vitalismus,”(87) in which he directs his attention especially to criticising Bütschli’s defence of mechanism, the only problem to which prominence is given is the one with which we are here concerned. In spite of their brevity, these writings have given rise to much controversy, because what is peculiar to the two standpoints is described with precision, and the problem is clearly defined. His criticism had its starting-point in, and received a special impulse from an empirical proof, due to a very happy experiment of his own, of the marvellous regenerative capacity, and the inherent purposive activity of the living organism. He succeeded in proving that if the lens of the eye of the newt be excised, it may be regrown. The importance of this fact is greatly increased if we trace out in detail the various impossible rival mechanical interpretations which have grown up around this interesting case. As Driesch says, “It is not a restoration starting from the wound, it is a substitution starting from a different place.” The Views of Botanists Illustrated.