II. COMING now to the large and important question of the Conjugation of Infusoria, its nature and bearing upon the life-history of the forms, we are bound to state at once our conviction of the inefficiency of the observations recorded on account of their discontinuity. Nothing but a close and continuous observation of the same forms extending over an entire life cycle, repeated again and again, can lead to absolute results. Errors fatal to the interests of truth inevitably arise, when minute organic forms are studied, not by continuous watching, but from inferences made from the phenomena manifest at different periods, the intervals between which are blank. Further, whilst the use of reagents on the dead forms taken at various stages is of the utmost value, when they are examined side by side with continuous observation on the living form, these may be not only not instructive but misleading when taken by themselves. Butschli on the Earliest Developmental Processes of the Ovum, and on the Conjugation of Infusoria. Studien uber die ersten Entwicklungsvorgange der Eizelle, die Zelltheilung und die Conjugation der Infusorien. Von O. Butschli. (Frankfurt, 1876.).