While the palæontological facts afford complete and abundant proofs of the modifying action of changes in the environment, Hyatt, in 1877, from his studies on sponges,[214] shows that the origin of their endless forms "can only be explained by the action of physical surroundings directly working upon the organization and producing by such direct action the modifications or common variations above described." Mr. A. Agassiz remarks that the effect of the nature of the bottom of the sea on sponges and rhizopods "is an all-important factor in modifying the organism."[215] While Hyatt's studies were chiefly on the ammonites, molluscs, and existing sponges, Cope was meanwhile at work on the batrachians. His _Origin of Genera_ appeared shortly after Hyatt's first paper, but in the same year (1866). This was followed by a series of remarkably suggestive essays based on his extensive palæontological work, which are in part reprinted in his _Origin of the Fittest_ (1887); while in his epoch-making book, _The Primary Factors of Organic Evolution_ (1896), we have in a condensed shape a clear exposition of some of the Lamarckian factors in their modern Neolamarckian form. In the Introduction, p. 9, he remarks: "In these papers by Professor Hyatt and myself is found the first attempt to show by concrete examples of natural taxonomy that the variations that result in evolution are not multifarious or promiscuous, but definite and direct, contrary to the method which seeks no origin for variations other than natural selection. In other words, these publications constitute the first essays in systematic evolution that appeared. By the discovery of the paleontologic succession of modifications of the articulations of the vertebrate, and especially mammalian, skeleton, I first furnished an actual demonstration of the reality of the Lamarckian factor of use, or motion, as friction, impact, and strain, as an efficient cause of evolution."[216] The discussion in Cope's work of kinetogenesis, or of the effects of use and disuse, affords an extensive series of facts in support of these factors of Lamarck's. As these two books are accessible to every one, we need only refer the reader to them as storehouses of facts bearing on Neolamarckism. The present writer, from a study of the development and anatomy of Limulus and of Arthropod ancestry, was early (1870)[217] led to adopt Lamarckian views in preference to the theory of Natural Selection, which never seemed to him adequate or sufficiently comprehensive to explain the origin of variations.