A rough periodicity may sometimes be seen in the progress of Science. After a stirring time of advance may come a period of lethargy, or even of negation, followed again by some fresh spurt of activity. At the present moment we seem to have reached a phase of negation in respect of the achievements of phyletic Morphology, and in conclusions as to Descent. This is suggested by the Presidential Address in Section K at the British Association at Liverpool. Already Professor Seward in the Hooker Lecture, 1922, had said, “It may be that we shall never piece together the links of the chain of life, not because the missing parts elude our search, but because the unfolding in all its phases cannot be compared to a single chain. Continuity in some degree there must have been, but it is conceivable that plant life viewed as a whole may best be represented by separate and independent lines of evolution, or disconnected chains which were never united, each being initiated by some revolution in the organic world.”