The Hydroids of the Scottish National Antarctic Expedition. By James Ritchie, 

 M.A., B.Sc., Fullerton Scholar, University of Aberdeen. Communicated by 

 W. S. BRUCE, F.R.S.E. (With Three Plates.) 



(MS. received May 1, 1906. Read June 21, 1906. Issued separately March 16, 1907.) 



The collection of Hydroids hereafter described was made in the years 1902-4 by 

 the Scottish National Antarctic Expedition ship Scotia, during her cruises in Antarctic 

 and sub-Antarctic seas. 



For the opportunity of examining the specimens I am indebted to Mr W. S. BRUCE, 

 the energetic leader of the expedition ; and I also wish to thank Professor J. ARTHUR 

 THOMSON for much assistance and advice in the course of my work. 



The collection, as here described, contains 41 specimens, of which 33 are referable 

 to 27 known species distributed among 15 genera, some of them being new varieties; 

 while the remainder have required the establishment of 7 new species and 1 new 

 genus. One specimen remains specifically undetermined. Thus there are in all 18 

 different genera, represented by 35 different species. 



Before dealing with the detailed systematic aspect of these forms, a few general 

 notes may be inserted : 



(1) The habitat of the forms shows considerable diversity. Sixteen of the speci- 

 mens were associated with Alcyonarians, being found along with, or growing upon, 

 those forwarded to Professor THOMSON for identification ; eight occurred upon larger 

 Hydroids ; while two were creeping upon seaweed fronds. Sponges formed the 

 foundation upon which several of the remaining colonies were erected. 



(2) With the specimens were associated many types of life. Frequent 

 diatoms and foraminifera lay within the hydrothecse or upon the stems ; various 

 sponges rested upon or surrounded some of the branches ; and there were also 

 numerous climbing or encrusting polyzoa, a few cirripede galls, and occasional 

 pycnogonids. 



(3) Of new forms described the most interesting is one of those rare types, apart 

 from the Plumularians, in which distinct nematophore structures have been found 

 (ALLMAN, 1883, p. 6 ; QUELCH, 1885, p. 4), and for it we have formed a new genus, 

 which we have named Brucella in honour of Mr BRUCE. The beautiful, highly 

 specialised coppinia-gonosome of this type indicates close affinities with the family 

 Lafoeidse in which it has been placed. 



(REPRINTED FROM THE TRANSACTIONS OP THE ROYAL SOCIETY OF EDINBURGH, VOL. XLV., pp. 519-545.) 



