THE STRUCTURE OF XENIA HICKSONI. 213 



Schenk (1896) mentions the occurrence of buds in eight new speeies 

 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 there- 

 fore Heteroxenia Elizabethan does not exhibit dimorphism ; hence he 

 renames it Xenia Elizabethce, 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 Xeniidce is not yet deter- 

 mined. 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 Bourne is that they are of two kinds, some being 

 young polyps and others quite different individuals, termed zooids. 



With a view to coming to some definite conclusion regarding the 

 nature of these small individuals, I have examined them in the specimen 

 of Xenia Hicksoni in great detail. I have also examined the sixteen other 

 specimens of Xenia at my disposal, and a specimen of the Heteroxenia 

 which Bourne has described and figured. These will be briefly 

 described below. 



External Characters op the Buds of Xenia Hicksoni. 



In Xenia Hicksoni the small individuals are all buds or young 

 polyps, as in this one specimen every stage in development may be 

 seen, from the youngest polyp only '32 mm. in length to the large 

 adult polyp 12 mm. long; and the series is perfectly complete, there 

 being no break at any point which would justify the division of the 

 individuals into two kinds. 



