ii THE VOYAGE OF H.M.S. CHALLENGEE. 
standpoint of our present knowledge, in the hope that a higher morphological interest, 
might he added to a work which would otherwise have contained little more than 
descriptive and distributional details. 
Two or three species have by an oversight received names which had been already 
appropriated. In the Explanation of the Plates, however, and in the Index, legitimate 
names have been substituted for those previously used, while the latter have been 
retained between brackets, and it is hoped that all danger of confusion will be thus 
avoided. The magnified figures contained in the Plates have been all drawn by the 
author, and in almost every instance those which represent the natural size of the 
species by Miss M. M'Daniel. 
' To Mr. John Murray, the Director of the Literary Staff of the Expedition, my best 
thanks are due for the readiness with which he acceded to everything which might 
facilitate my work, for the courtesy which I received from him throughout, and for the 
patience with which he met the somewhat tardy appearance of the Report. To Mr. 
William E. Hoyle I am also much indebted for valuable assistance in the verification 
of localities, and in the general supervision of the proofs. 
CONTENTS. 
PAGE 
GENERAL INTRODUCTION, iii 
SKETCH OF THE MORPHOLOGY AND LIFE HISTORY OF THE HYDROIDA, . . v 
I. Fundamental Form — General Architecture of the Hydroida, v 
II. Disposition of the Fundamental Layers, ...... vi 
III. Diversity of Form and Function in the Buds, ..... vii 
IV. Histology of the Fundamental Layers, ....... viii 
1. The Endoderm, . . . . . . ■ . . . viii 
2. The Ectoderm, . . . . . . . . xi 
3. The Mesosarc, .......... xxiii 
4. The Perisarc, . . . . . . . . . xxiv 
V. The Gonosome, .......... xxv 
1. The Gonophore, . . . . . ■ . . . . xxvi 
2. Origin of the Generative Elements, . . . . . . xxxiii 
3. Development of the Ovum, ........ xxxvi 
PRIMARY MODIFICATIONS OF FORM— CLASSIFICATION OF THE HYDROIDA, . xlix 
Tabular View of the Leading Systematic Groups of the Order Hydroida, . . Iii 
DISTRIBUTION, ........... liv 
Station List, ........... lxii 
Geographical and Bathymetrical Distribution of the Species, .... Ixviii 
DESCRIPTION OF GENERA AND SPECIE^, ....... 1 
Gymnoblastea — B ougainvillidae, 1 ; Eudendridse, 2 ; Monocaulidse, 5, . . . . 1 
Calyptoblastea — H aleciidae, 8 ; Campanularidse, 18 ; Perisiphonidse, 32 ; Grammaridse, 46 ; 
Sertularidie, 49 ; Idiidse, 82, ........ 8~ 
INDEX, 89 
EXPLANATION OF THE PLATES. 
