THE LAST LINK OUR PRESENT KNOWLEDGE OF THE DESCENT OF MAN BY ERNST HAECKEL (JENA) WITH NOTES AND BIOGRAPHICAL SKETCHES BY HANS GADOW, F.R.S. (CAMBRIDGE) LONDON ADAM AND CHARLES BLACK 1898 CONTENTS PAGE THE LAST LINK INTRODUCTORY 1 COMPARATIVE ANATOMY 8 PALÆONTOLOGY 20 OTHER EVIDENCE 42 STAGES RECAPITULATED 47 BIOGRAPHICAL SKETCHES: LAMARCK, SAINT-HILAIRE, CUVIER, BAER, MUELLER, VIRCHOW, COPE, KOELLIKER, GEGENBAUR, HAECKEL 80 THEORY OF CELLS 115 FACTORS OF EVOLUTION 117 GEOLOGICAL TIME AND EVOLUTION 135 NOTE The address I delivered on August 26 at the Fourth International Congress of Zoology at Cambridge, 'On our Present Knowledge of the Descent of Man,' has, I find, from the high significance of the theme and the general importance of the questions connected with it, excited much interest, and has led to requests for its publication. Hence this volume, edited by my friend Dr. H. Gadow, my pupil in earlier days, who has not only revised the text, but has also enriched it by many valuable additions and notes. ERNST HAECKEL. _Jena, December, 1898._ THE LAST LINK At the end of the nineteenth century, the age of 'natural science,' the department of knowledge that has made most progress is zoology. From zoology has arisen the study of transformism, which now dominates the whole of biology. Lamarck[1] laid its foundation in 1809, and forty years ago Charles Darwin obtained for it a recognition which is now universal. It is not my task to repeat the well-known principles of Darwinism. I am not concerned to explain the scientific value of the whole theory of descent. The whole of our biological study is pervaded by it. No general problem in zoology and botany, in anatomy and physiology, can be discussed without the question arising, How has this problem originated? What are the real causes of its development? [1] See note, p. 80.