ELEMENTS OF COMPARATIVE ANATOMY. BY CARL GEGENBAUR PROFESSOR OF ANATOMY AID DlRECTOR OF TUB ANATOMICAL INSTITUTE AT HXIDXLBEBCt. TRANSLATED BY F. JEFFREY BELL, B. A., MAGDALBIC COLLEGE, OXPORD. THE TRANSLATION REVISED AND A PREFACE WRITTEN BY E. RAY LANKESTER, M. A., F. R. S., FELLOW OFEXETER COLLEGE, OXFORD, AND PROFESSOR OF ZOOLOGY 1878. PREFACE TO THE SECOND EDITION. Our knowledge has been so much increased in extent and exactness in almost every department of Comparative Anatomy since the time when I converted into the first edition of this smaller manual the Grundriss that the publication of a second edition hardly seemed an easy task. Nevertheless, I gladly undertook it, for I had observed so much new evidence of the importance of the doctrine of development in anatomical inquiry The road along which science may travel forward success fully seems indeed to be growing easier, yet the distance which we have made is but short in comparison with that which lies in front of us, and far beyond our view. Every question solved leads again to fresh problems, and renders unstable even what seemed to have taken a definite form. There are, therefore, great difficulties in giving such a comprehensive presentation of the subject as a text-book ought to supply I have tried as much as possible to evade these difficulties where I have been unable to overcome them. Much remains unaltered, because recent investigations appear to demand fundamental changes, the concrete expression of which cannot be immediately taken in hand. I have somewhat modified the arrangement of the matter. I can hardly be blamed for separating the Brachiopoda from the Mollusca, and treating them as forming an independent phylum. Nor indeed is the change a real one, for even in my Grundziige I drew especial attention to the great difference that obtained between them and the other Mollusca The Tuuicata have been treated in tho same way, but this does not require any apology at the present date. By treating the subject more concisely I have been able to increase the real matter to a certain extent, without enlarging tho size of tho book. I have, of course, only dealt with what has seemed to me to be of capital importance many, and even important, details have been omitted, owing to tho limits imposed by the aim of the book. I have endeavoured to correct some previous mistakes and to supply omissions. If any such have been retained, or have newly crept in, I shall bo fairly judged, I know, by anatomists, who will remember the vast extent of our science and tho object of this work. I hope that I have satisfied them, and if I have my toil is well repaid. Heidelberg, November, 1877. O. Gegenbaur. PREFACE TO THE ENGLISH TRANSLATION. IT is a great pleasure to me to be able to place in the hands of my pupils in Oxford and London an English translation of Professor IEGENBAURS Grundriss der Vergleieheiiden Anatomie. I have to thank the energy and industry of Mr. JEFFREY J ELL, of Magdalen College, Oxford now one of the staff of the British Museum, for the translation which lie undertook and carried through at my request, when I found that my time was too fully occupied with other work to allow of my completing it myself within a sufficiently short period from the date-of publication of the German work. My share of the present work has therefore consisted in a careful revision of the MS. and proof-sheets, which has been by no means a mere formality, but enables me to give the assurance that the original work is faithfully rendered in the translation. The chapter on the Tunicata I took occasion to translate myself. That Professor GEGENBAURS work will be of great service to those English students who do not already read German cannot be doubted...