282 J. H. ASHWORTH. 



Bourne is that they are of two kinds, some being young polyps 

 and others quite diflfereut 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 of 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 develop- 

 ment 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. 



The buds are invariably found on the edge of the arched 

 end of the stem. Their numbers vary on different stems, 

 there being usually from six to ten buds less than 3 mm. long 

 on each stem (PI. 23, fig. 1, left). The smallest bud (PI. 24, 

 figs. 4, 4a) measures "32 mm. in length and "44 mm. in width. 

 It is situated just under the edge of the umbellate summit of 

 the stem. It is a short cylindrical outgrowth, at the distal end 

 of which the developing tentacles are indicated as eight small 

 rounded lobes about "1 mm. long, divided from each other by 

 shallow furrows. A slight depression in the centre of the distal 

 end indicates the position of the future mouth, which is not yet 

 open to the exterior. The tentacles increase in length rather 

 more rapidly proportionately than the body of the polyp. In 

 the smallest specimen they are less than one third the total 

 length of the polyp, but in rather larger polyps they form from 

 two fifths to one half the total length of the polyp. The 

 tentacles remain simple lobes until the polyps attain a length 

 of nearly 1 mm. In a specimen "95 mm. long (fig. 5) the 



