478 SYDNEY J. HICKSON. 



Famil} Xeniidae. 



Genus Xenia. Savigny. 



In writing upon this genus I must explain that I do not inchide in it those species 

 which belong to the genus Heteroxenia of KiiUiker. This explanation is necessary in view 

 of the recently published paper by Kiikenthal (16) in which the proposal is again brought 

 forward to merge Heteroxenia into Xenia. 



The genus Heteroxenia was established by KoUiker for a species found at Port Denison 

 in Australia which exhibited dimorphism, and was named Heteroxenia Elisabethae. Klun- 

 zinger (14) in 1879, upon the examination of some specimens of Xenia fuscescens which he 

 found in the Red Sea, threw some doubt on the validity of the genus Heteroxenia. 



Up to this point no detailed account had been given of the structure of the small 

 polyps which Kolliker regarded as siphonozooids, and it was a question whether they were 

 really siphonozooids or young polyps not yet developed into their adult form. 



In 1895 G. C. Bourne (4) examined and described the siphonozooids of a specimen of 

 a species which he attributed to Heteroxenia Elisabethae (Kiill.) from Zanzibar, and Ashworth (1) 

 subsequently examined the same specimen and confirmed Bourne's determination of the species. 



Both Bourne and Ashworth made careful anatomical examinations of the specimen, 

 studying in minute detail and with the best histological methods the structure of the 

 siphonozooids, and they came to the conclusion that there are true siphonozooids in this 

 species, and that they can be distinguished without difficulty from young autozooids. It 

 does not appear from Kukenthal's recent paper that he has made any anatomical investi- 

 gation of a species of Heteroxenia, and the arguments used in defence of his proposal 

 show no advance on those of Klunzinger which were considered and rejected by Bourne 

 and Ashworth. 



Whether the specimens collected by Klunzinger in the Red Sea, and named by him 

 Xenia fuscescens Ehr., are or are not identical with Heteroxenia Elisabethae is a point 

 upon which I will not venture to express an opinion, but I cannot refrain from saying 

 that it is premature at present to assert that they are. I cannot therefore accept Kukenthal's 

 view that the genus Heteroxenia should be suppressed. It is unfortunate that no specimens 

 of a dimorphic Xeniid are to be found in Mr Gardiner's collection, and that only eight 

 specimens of one species of Xenia were discovered in the Maldives. At present therefore 

 it appears that the genus Heteroxenia is confined to the exceptionally hot waters of 

 N. Australia, the Red Sea, and Zanzibar, together with one species Heteroxenia capensis 

 ■with distinct characters from cooler water off S. Africa. 



No specimens have yet been observed in the extensive collections of Alcyonaria that 

 I have examined fi-om the Maldives, Ceylon, Singapore, and the Malay archipelago. If, by 

 any chance, the single specimen of Heteroxenia Elisabethae in the Museum Godeffroy, which 

 Kolliker examined, was wrongly labelled, and did not originally come from Port Denison 

 in Australia, the geographical distribution of the genus might not seem so extraordinary 

 as it is. It is true there is no definite reason for doubting the locality of Kolliker's 

 specimen, but it is noteworthy that notwithstanding the careful investigations of Saville 



