THE STRUCTURE OP XENIA HIOKSONI. 281 



(1) The larger polyps with well-developed tentacles, witli 

 three rows of lateral pinnules on their margins, their coelentera 

 continued to the bottom of the stem or nearly so, and filled 

 with ova. At the edges of the arched end of the stem there 

 were numerous young polyps in all stages of development, 

 many of which showed distinct pinnules on their tentacles. 



(2) Closely applied sterile zooids which have no tentacles, 

 but only eight radiate lobes round the mouth. The coelentera 

 of these individuals extend only a little way into the stem, and 

 then communicate with the coelentera of the polyps by anasto- 

 mosing endoderraic canals. Among these zooids there are 

 never any individuals which show signs of pinnate tentacles nor 

 which contain gonads. Bourne concludes that in this form 

 there is distinct dimorphism. 



Schenk (1896) mentions the occurrence of buds in eight 

 new species of Xenia from Ternate, which he has described. 

 He briefly describes the external characters of the buds in 

 Xenia viridis, and figures three stages of development. 

 The first figure represents a small bud about 3 mm. long, in 

 which the tentacles are simple finger-shaped lobes. The other 

 two are drawings of slightly larger polyps the tentacles 

 of which bear, in one case six, and in the other about twelve 

 pinnules on each side of the tentacle (seen from the outer 

 side). In all the examples mentioned by Schenk the small 

 individuals are young polyps in course of development, as 

 pinnules have already appeared on the tentacles of many of 

 them. Schenk (loc. cit., p. 53) remarks that he believes the 

 zooids of Kolliker are merely young polyps, and therefore 

 Heteroxenia Elizabethae does not exhibit dimorphism; 

 hence he renames it Xenia Elizabethse, and places it near 

 X. fuscescens, Klunzinger. Thus Schenk supports Haacke's 

 view that there is no dimorphism of the polyps of Xenia. 



From this short account of previous observations it will be 

 seen that the nature of these small individuals in the Xeniidse 

 is not yet determined. That they are all buds or young 

 polyps is strongly affirmed by Klunzinger, Haacke, Wright 

 and Studer, and Schenk; while the opinion of Kolliker and 



