OF
VOL. II.
Memorial Edition.
Cambridge:
PRINTED BY C. J. CLAY, M.A. AND SON,
AT THE UNIVERSITY PRESS.
Memorial Edition.
M.A., LL.D., F.R.S.,
FELLOW OF TRINITY COLLEGE,
AND PROFESSOR OF ANIMAL MORPHOLOGY IN THE UNIVERSITY OF
CAMBRIDGE.
EDITED BY
M. FOSTER, F.R.S.,
PROFESSOR OF PHYSIOLOGY IN THE UNIVERSITY OF CAMBRIDGE;
AND
ADAM SEDGWICK, M.A.,
FELLOW AND LECTURER OF TRINITY COLLEGE, CAMBRIDGE.
VOL. II.
A TREATISE ON COMPARATIVE EMBRYOLOGY.
Vol. I. Invertebrata.
London:
MACMILLAN AND CO.
1885
[The Right of Translation is reserved.]
My aim in writing this work has been to give such an account of thedevelopment of animal forms as may prove useful both to students andto those engaged in embryological research. The present volume, savein the introductory chapters, is limited to a description of thedevelopment of the Invertebrata: the second and concluding volume willdeal with the Vertebrata, and with the special histories of theseveral organs.
Since the work is, I believe, with the exception of a small but usefulvolume by Packard, the first attempt to deal in a complete manner withthe whole science of Embryology in its recent aspects, and since alarge portion of the matter contained in it is not to be found in theordinary text books, it appeared desirable to give unusually amplereferences to original sources. I have accordingly placed at the endof each chapter, or in some cases of each section of a chapter, a listof the more important papers referring to the subject dealt with. Thepapers in each list are numbered continuously, and are referred to inthe text by their numbers. These lists are reprinted as an appendix atthe end of each volume. It will of course be understood that they donot profess to form a complete bibliography of the subject.
[Pg vi]In order to facilitate the use of the work by students I have employedtwo types. The more general parts of the work are printed in largetype; while a smaller type is used for much of the theoretical matter,for the details of various special modes of development, for thehistories of the less important forms, and for controversial mattergenerally. The student, especially when commencing his studies inEmbryology, may advantageously confine his attention to the matter inthe larger type; it is of course assumed that he already possesses acompetent knowledge of Comparative Anatomy.
Since the theory of evolution became accepted as an establisheddoctrine, the important bearings of Embryology on all morphologicalviews have been universally recognised: but the very vigour with whichthis department of science has been pursued during the last few yearshas led to the appearance of a large number of incomplete andcontradictory observations and theories; and to arrange these intoanything like an orderly and systematic exposition has been no