[In 1868 he published five scientific memoirs, amongst them his classification of birds and "Remarks upon Archaeopteryx Lithographica" ("Proceedings of the Royal Society" 16 1868 pages 243-248). This creature, a bird with reptilian characters, was a suggestive object from which to popularise some of the far-reaching results of his many years' labour upon the morphology of both birds and reptiles. Thus it led to a lecture at the Royal Institution, on February 7, "On the Animals which are most nearly intermediate between Birds and Reptiles." Of this branch of work Sir M. Foster says: (Obituary Notice "Proceedings of the Royal Society" volume 59):-- One great consequence of these researches was that science was enriched by a clear demonstration of the many and close affinities between reptiles and birds, so that the two henceforward came to be known under the joint title of Sauropsida, the amphibia being at the same time distinctly more separated from the reptiles, and their relations to fishes more clearly signified by the joint title of Ichthyopsida. At the same time, proof was brought forward that the line of descent of the Sauropsida clearly diverged from that of the Mammalia, both starting from some common ancestry. And besides this great generalisation, the importance of which, both from a classificatory and from an evolutional point of view, needs no comment, there came out of the same researches numerous lesser contributions to the advancement of morphological knowledge, including among others an attempt, in many respects successful, at a classification of birds. This work in connection with the reptilian ancestry of birds further appears in the paleontological papers published in 1869 upon the Dinosaurs (see Chapter 23), and is referred to in a letter to Haeckel. His Hunterian lectures on the Invertebrata appeared this year in the "Quarterly Journal of Microscopical Science" (pages 126-129, and 191-201), and in the October number of the same journal appeared his famous article "On some Organisms living at great depth in the North Atlantic Ocean," originally delivered before the British Association at Norwich in this year (1868). The sticky or viscid character of the fresh mud from the bottom of the Atlantic had already been noticed by Captain Dayman when making soundings for the Atlantic cable. This stickiness was apparently due to the presence of innumerable lumps of a transparent, gelatinous substance, consisting of minute granules without discoverable nucleus or membranous envelope, and interspersed with cretaceous coccoliths. After a description of the structure of this substance and its chemical reactions, he makes a careful proviso against confounding the statement of fact in the description and the interpretation which he proceeds to put upon these facts:--]