212 J. H. ASHWORTH. 



appear to develop into fully-formed polyps, but to remain in the bud- 

 like stage, with short, simple, mostly incurled tentacles. They are 

 1 mm. to 2 mm. long and '5 mm. broad, and are cylindrical or club- 

 shaped. On account of the large numbers of these small individuals, 

 Klunzinger placed his Xenia fuscescens near the Heteroxenia Elizabethan 

 of Kolliker. There are no transition stages between these small indi- 

 viduals which do not appear to develop into larger polyps and the 

 adult polyps, and from the description and figures they appear to be 

 quite as distinct as the two kinds of individuals described by Kolliker 

 in Heteroxenia. 



Haacke (1887), who examined some of the Xeniidce in Torres Straits,, 

 says that the small individuals are merely young polyps, and all stages 

 of development between them and the adult polyps may be met with. 

 Therefore he denies the occurrence of heteromorphism in the Xeniidas. 



Wright and Studer in the ' Challenger Report ' (1889) record the 

 observations of Klunzinger and Haacke noticed above. They agree 

 with Haacke, and therefore propose the provisional abandonment of 

 Kolliker's genus Heteroxenia. 



Bourne (1895) observed in his new species, Xenia Garc\o j , numerous 

 imperfect polyps or buds in all stages of growth at the edge of the 

 polyp-bearing summits of the stems. He remarked that " these are 

 not siphonozooids, but stunted or developing polyps." 



Bourne also described a specimen which he referred provisionally 

 (being unable to procure Kolliker's original description) to the species 

 Heteroxenia Elizabethce. In his description were noted : — 



(1) The larger polyps with w T ell-developed tentacles, with 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 indi- 

 viduals extend only a little way into the stem, and then communicate 

 with the coelentera of the polyps by anastomosing endodermic 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. 



