THE 
VOYAGE OF H.M.S. CHALLENGER. 
ZOOLOGY. 
REPORT on the Hydroida dredged by H.M.S. Challenger during the Years 
1873-76. By Professor G. J. Allm an, M.D., LL.D., F.R.C.S.I., F.R.SS. 
L. & E., M.R.I.A., C.M.Z.S., Mem. Roy. Danish Acad. Sci., &c. 
W x. 
PART II.— THE TUBULARIJSLE, CORYMORPHINJE, CAMPAJSTU- 
LARIM1, SERTULARIALE, AND THALAMOPHORA. 
PREFACE. 
The collection of Hydroida brought home by the Challenger contains representatives of 
almost every important group of this order. The Plumularinse, to which I have devoted 
a separate examination in that part of the Report which has been already published, are 
richly represented in the collection, and examples of almost all the leading types of this 
beautiful group have been found in it. Many of these have afforded the means of 
working out certain morphological relations which throw light on the architecture of 
the group and demonstrate a fundamental unity amongst very diverse modifications of 
structure. The Hydrocorallinse have been made the subject of a very valuable inde- 
pendent Report by Professor Moseley , 1 and it is now proposed to consider all the 
remaining Hydroid groups, examples of which were obtained during the Expedition. In 
addition to the new species certain previously known ones have been figured, when this 
seemed desirable. 
I have taken advantage of the opportunity afforded by the typical character of the 
collection to make this the basis of a general exposition of Hydroid morphology, from the 
1 Report on certain Hydroid, Alcyonarian, and Madreporarian Corals, Zool. Chall. Exp., part vii. 
(zool. chall. exp. —part lxx. — 1888.) Aaaa a 
