700 
MR. S. J. HICKSON ON THE CILIATED GROOVE 
appreciated, but I do so in order to point out the part which the presence or absence 
of a siphonoglyphe may play in the arrangement of the group, and some other points 
upon which the classification may turn. 
There can be little doubt, I think, that the ancestral form of the Alcyonaria was 
not colonial, but was a simple isolated individual differing but slightly from the 
isolated genera which exist at the present day. 
The fact that the three genera of isolated Alcyonaria are remarkably ra.re, present 
but few species, and have a wide geographical distribution (Monoxenia, coast of 
Arabia, Haimea, Fiji Islands, and Hartea, west coast of Ireland), point to the 
conclusion that they are the representatives of an ancient group which may have 
been much larger than it is now. 
It might therefore be advisable to separate these genera as a distinct group, which 
might be called the Proto-alcyonaria. 
The next step in the phylogeny was the formation from such an isolated ancestor 
of a colony. The formation of the colonies may have taken jfiace in two ways : 
first, by the formation of buds from the first formed polyp; and secondly, by the 
intermediation of a stolon upon which the young buds were formed. 
A colony formed in this second way would with slight modifications give us a form 
such as our modern Clavularia or Cornularia. 
In the genus Tubipora there is a stolon which I shall point out in a subsequent 
paper is very similar to the stolon of Clavularia. Tubipora might in fact have been 
derived from a Clavularia-Yike ancestor, in which the following modifications took 
place : The polyps became considerably elongated, and the spicules of the body-wall 
fused together to form a hard tubular support for them. These long polyps then 
became connected by canals which eventually joined together to form the horizontal 
platforms traversed by a network of the canals, and from them new polyps budded as 
they do from the original stolon. 
If this reasoning is subsequently proved to be accurate it will be necessary to 
separate those forms with a stolon from the rest of the Alcyonaria into a separate 
group, which might be called the Stolonifera. 
In the great majority of the Alcyonaria we have sufficient evidence, I think, to 
prove that they are formed by budding from the first-formed polyps which usually 
remain in the centre of the colony. 
Taking a hypothetical ancestor, x, which probably had a conformation somewhat as 
follows : A central large polyp from which sprung, in a fan-shaped manner, a number 
of lateral buds of which those nearest the central polyp were the largest, we should 
have the rest of the Alcyonaria formed from it by modifications in several directions. 
In one direction we have the well-marked group of the Pennatulida. This group 
probably sprang from the ancestral stock at a very remote period, as is shown by the 
changes which have taken place in the central polyp, the arrangement of the 
subsequently formed polyps upon it, and the complete and universal dimorphism of 
