128 



Rhabdopleura nornmni has alread)' been referred to in this Report on p. 8 (coenoecium), 

 on pp. 52, 78 (stalk), on pp. 81, 87 (reproductive organs), and on p. 92 (budding). .Should the 

 genus include more than one species it may, however, be questioned whether the form described 

 by FowLER from Tristan d'Acunha is really identical with A'. nornmni. 



XX. SUMMARY OF THE PRINCIPAL RESULTS. 



(i). The geographical and bathymetrical range of Cephalodiscns are largely extended by the 

 description of three new species from Oriental waters, one of them [C. gracilis) having 

 been obtained, at or near low tide mark, on a Coral Reef on the coast of Borneo. The 

 second [C. sibogae) is from 75 — 94 metres off the S.E. point of Celebes, while the third 

 (C. levinseni) is from about 183 metres at the S. end of the Corea Strait. 



(2). While the specimens of C. gracilis and C. leidnseni resemble the "Challenger" specimens 

 of the type-species [C. dodecalopJius) in consisting exclusively of female inciividuals, that of 

 C. sibogae is of the male sex. The possibility is not excluded that C. sibogae may be the 

 male of C. gracilis \ but it is concluded that it is really a distinct species. 



(3). The colony of C. sibogae offers a striking case of dimorphic zooids. Certain individuals are 

 of the type characteristic of a female Cephalodisc7is except for the absence of gonads. 

 These are termed neuters, and they doubtless provide for the nutrition of the colonv. 

 The remaining individuals are males, and are remarkable for the vestigial nature of the 

 apparatus connected with the coUection and digestion of food. Their curiously modified 

 arms are reduced to a single pair, which are not provided with tentacles ; the operculum 

 is absent; and the alimentary canal is in a ve.stigial condition. The jjrincipal organs are 

 a pair of large testes, which correspond in the position of their external apertures and in 

 their relation to the dorsai vessel with the ovaries of the females of other species. The 

 proboscis is well developed, while the central nervous system, the bodv-cavities, the collar- 

 canals and the vascular s)stem resemble those of an ordinar)- Cephalodiscns. Their nutrition 

 is probably provided for by vascular connexions with the neuter individuals. 



(4). The characters of the coenoecium are shewn to be of importance in discriminating 

 the species. 



(5). The zooids (jf the several species, while differing from one another to a marked extent 

 in form, in the number of their tentacular arms, and in the characters of their stalk, are 

 strikingly uniform in all essential points of structm-e. 



(6). The arms and operculum are regarded as modifications of the anterior free edge of the 

 collar. The number of arms of the female or neuter zooids ranges from four pairs in 

 C. sibogae to six jjairs in C. dodecalophns and C- levinseni \ C. gracilis occupying an 

 intermediate position in possessing five pairs of arms. 



