Cuvier's memorable descriptions of the extinct vertebrates of the Paris basin had founded the new science of Palæontology, and though neither he nor anyone else was aware of the fact, had made it possible to trace, very imperfectly no doubt, the descent of a few modern ungulates. Lyell's _Principles of Geology_ (1830-3) had shaken the belief in catastrophes repeatedly breaking the succession of life on the earth. It was rapidly becoming impossible to maintain that the account of creation given in the book of Genesis was even approximately accurate. In the year 1828 Baer had almost made up his mind that the facts of development pointed to a common plan of structure, perhaps to a common origin, for each of the great types of animal life.[43] Darwin's _Journal_ had appeared in 1839, and though the explanations which it offered were not inconsistent with prevalent opinion, evolutionary suggestions were introduced into the second edition of 1845. Lyell at least was already aware that the voyage of the _Beagle_ had impelled Darwin to examine afresh the accepted philosophy of creation. Between 1840 and 1850 faint signs of coming change struck orthodox reasoners with misgiving and gave increased confidence to free-thinkers. A few German botanists and zoologists declared against the immutability of species. The _Vestiges of the Natural History of Creation_, which might be called a premature explosion, dates from 1844. Hofmeister (see supra, p. 109) put forth a detailed comparison of the flowering plants with the higher cryptogams, which strongly suggested a theory of descent with modification, and is unintelligible on any other basis. He indicated no such interpretation himself, being content to establish the new homologies; but the _Origin of Species_, as soon as it appeared, commanded his entire sympathy. Among those who rejected fixity of species and special creation before 1859 none was so clear or so outspoken as Herbert Spencer, who thought out for himself an evolutionary philosophy which was not shaken by Darwin. It is impossible to discuss in this place the question whether or not it was shaken by Weismann.