This is a collection of research reports, principally by Willstätter's pupils, and general addresses by Professors Willstätter himself. The two volumes contain reprints of 139 such papers and addresses already published in the scientific journals. In this series appear research reports on the chemistry and action of practically the entire series of plant and animal enzymes with the exception of pepsin. The collection will be useful for laboratory and research men; but, since the original reports are virtually reprinted without change, there is a good deal of duplication, especially in the way of literary citations and discussions. This makes the collection unnecessarily voluminous and consequently expensive.