Unger’s text-book ‘Anatomie und Physiologie der Pflanzen’ (1855) was superior in conception and execution. It introduced the beginner to the doctrine of cells with careful attention to all that was known on the subject, if sometimes with some hastiness of decision, while it brought the really important points everywhere into prominence and employed individual facts to explain the general propositions, as should always be done in a work intended for learners. But in addition to this Unger’s book contained much that was really new and valuable, and among other things some very important remarks on the physiological characteristics of protoplasm; and it pointed out for the first time the similarity between vegetable protoplasm and the sarcode in Rhizopods, which Max Schulze had before carefully described. In this year Nägeli also published investigations into the primordial utricle and the formation of swarmspores in his ‘Pflanzenphysiologische Untersuchungen,’ Heft I, which gave a new insight into the physical and physiological characteristics of protoplasm. It has been mentioned above that De Bary’s investigations into the Myxomycetes in 1859 had thrown new light on the subject of protoplasm, and had called attention to vital phenomena connected with it, which, though analogous to what had been before observed, were rendered very striking from the circumstance that in this case the protoplasm was not in microscopically small portions enclosed by firm cell-walls, but moved about and showed changes of shape in large, sometimes in very large, masses, that were entirely free and unconfined. Here was the best opportunity for making a nearer acquaintance with protoplasm and for learning to recognise it as the immediate support of all vegetable and animal life; in succeeding years the zootomists and physiologists Max Schulze, Brücke, Kühne, and others established the fact that the substance which lies at the foundation of cell-formation in animals agrees in its most important characteristics with the protoplasm of vegetable cells. A more detailed account of modern researches on this subject, which would moreover involve the examination of Hofmeister’s work of 1867, ‘Die Lehre von der Pflanzenzelle,’ does not fall within the limits of our history. 2. FURTHER DEVELOPMENT OF OPINION ON THE NATURE OF THE SOLID FRAMEWORK OF CELL-MEMBRANE IN PLANTS AFTER 1845.