viii PREFACE TO SECOND EDITION. 



many unforeseen interruptions. Under these circumstances it is my 

 pleasant duty to thank the Delegates of the University Press for their 

 kind forbearance on the question of time. 



My warmest thanks are due to Sir H. W. Acland, K.C.B., F.R.S., 

 for the use of a room belonging to his own suite in the University 

 Museum, and for a free and extensive command of all requisite literature 

 in that rich storehouse of scientific books, the Radcliffe Library, without 

 which my task could never have been accomplished. To Professor Moseley, 

 F.R.S., Dr. Rolleston's successor in the Linacre chair, I render my best 

 thanks for an unlimited employment of the anatomical collections under 

 his charge, and the loan of his own MS. notes on the Anthozoa Zoantharia. 

 I have also to record a debt of gratitude to my early and constant friend, 

 Professor Westwood, who has given me much assistance by way of access 

 to specimens and pamphlets on the difficult phylum Arthropoda. In kind 

 compliance with my request, Professor Ray Lankester, F.R.S., liberally 

 allowed me to copy two figures of his own construction (Woodcut 13, A, B, 

 and i, 2, 3, 4) ; and Professor Kitchin Parker, F.R.S., furnished valuable 

 information, at the time unpublished, relative to points in the development 

 of the Vertebrate skull, and also granted permission for the use of two 

 figures (Woodcuts, 6 and 7) illustrating the skull of the common Frog. 

 I have to thank Mr. C. Robertson, who was conversant with Professor 

 Rolleston's wishes, for assistance on various points, and Mr. G. C. Bourne 

 for several suggestions and for other help ; nor must I by any means 

 omit Professor W. B. Spencer of Melbourne University, and Mr. G. H. 

 Fowler, to whose most timely and friendly care I am entirely indebted 

 for the addition of the Index. 



The compilation of this book, though laborious in the extreme, has 

 been attended by its pleasures. But the crowning pleasure of all can only 

 befall me if its publication gains the sympathy of those who are com- 

 petent to judge the nature of the task, and the book itself proves a real 

 aid to students in this most fascinating science of Comparative Anatomy. 



WM. HATCHETT JACKSON. 



MUSEUM, OXFORD : 



September 24, 1887. 



