[454] "Die Polycladen," _Fauna u. Flora des Golfes von Neapel_, Monog. v., Leipzig, 1884, and "Beitraege zu einer Trophocoeltheorie," _Jen. Zeits._, xxxviii., pp. 1-373, 1904 (which see for a modern account of theories of metamerism). [455] "Die Abstammung der Anneliden u. Chordaten," _ Jen. Zeits._, xxxix., pp. 151-76, 1905. "The Gastrulation of the Vertebrates," _Q.J.M.S._, xlix., pp. 403-19, 1906. "Early Ontogenetic Phenomena in Mammals," _Q.J.M.S._, liii., pp. 1-181, 1909. CHAPTER XVII THE ORGANISM AS AN HISTORICAL BEING "Of late the attempt to arrange genealogical trees involving hypothetical groups has come to be the subject of some ridicule, perhaps deserved. But since this is what modern morphological criticism in great measure aims at doing, it cannot be altogether profitless to follow this method to its logical conclusions. That the results of such criticism must be highly speculative, and often liable to grave error, is evident." The quotation is from Bateson's paper of 1886, and it is symptomatic of the change which was soon to come over morphological thought. New interests, new lines of work, began to usurp the place which pure morphology had held so long. This is accordingly a convenient stage at which to take stock of what has gone before, to consider the relation of evolutionary morphology to the transcendental and the Cuvierian schools of thought which preceded it, and to make clear what new element evolution-theory added to morphology. The close analogy between evolutionary and transcendental morphology has already been remarked upon and illustrated in the last three chapters. We have seen that the coming of evolution made comparatively little difference to pure morphology, that no new criteria of homology were introduced, and that so far as pure morphology was concerned, evolution might still have been conceived as an ideal process precisely as it was by the transcendentalists. The principle of connections still remained the guiding thread of morphological work; the search for archetypes, whether anatomical or embryological, still continued in the same way as before, and it was a point of subordinate importance that, under the influence of the evolution-theory, these were considered to represent real ancestral forms rather than purely abstract figments of the intelligence. The law of Meckel-Serres was revived in an altered shape as the law of the recapitulation of phylogeny by ontogeny; the natural system of classification was passively inherited, and, by a _petitio principii_, taken to represent the true course of evolution. It is true that the attempt was made to substitute for the concept of homology the purely genetic concept of homogeny, but no inkling was given of any possible method of recognising homogeny other than the well-worn methods generally employed in the search after homologies.