matter is to be defined as "a unique chemical system, the molecules
of which, by their peculiar reciprocal action, give rise to psychical and
material processes in such a way that the processes of the one kind are
always causally conditioned and started by those of the other kind." The
psychical phenomena he regards as transcendental, supernatural,
"mystical," yet unquestionably also subject to a strict causal nexus,
although the causality must remain for ever concealed. Starting from this
basis, he analyses and rejects the explanations which have been offered in
terms of the analogy of ferments, enzymes, or catalytic processes. In
particular, he disputes Ostwald's "Energismus" and Verworn's Biogen
hypothesis.(85)

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 Wuerzburg, 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 Buetschli'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.

It might have been expected that in the domain of plant-biology, if
anywhere, the mechanisti