Thomas Henry Huxley

“ And all the facts of geology and palaeontology not only tend to show that the knowledge of ancestral development is likely long to remain fragmentary, but lead us to doubt, whether even such fragments as may be vouchsafed to us by the extension of geological inquiry will ever be sufficiently old, in relation to the whole duration of life on the earth, to give us positive evidence of the nature of the earliest forms of animals. ”

“ The only genus of animals of which we possess a satisfactory, though still not quite complete, ancestral history, is the genus Equus, the development of which in the course of the Tertiary epoch from an Anchitherioid ancestor, through the form of llipparion, appears to admit of no doubt. ”

“ In the place of assemblages of distinctly definable groups, which it has hitherto been the object of the Taxonomist to define and co-ordinate in precise logical categories, we are gradually learning to substitute series, in which all the modifications by which a fundamental form passes from lower to higher degrees of organic complication, are summed up. ”

“ Two animals belong to the same group, when they are similar in structure, personal development, and ancestral development, and not otherwise. Hence it follows that a perfect and final zoological classification cannot be made until we know all that is important con cerning 1, the adult structure ; 2, the personal develop ment ; and 3, the ancestral development of animals. It is hardly necessary to observe that our present knowledge, r.s regards even the first and second heads, is very imperfect ”

“ While holding the doctrine of evolution to its fullest extent, and having no doubt that Taxonomy ought to be the expression of ancestral development, or pkyloyeny, as well as of embryogeny and adult structure, and while con ceiving that the attempts at founding a scientific phylo- geny, which have been made by Haeckel and others, are of much interest and importance as guides to and suggcs- tors of investigation, the present writer looks upon all such attempts as provisional hypotheses ”