694 
MR. S. J. HICKSON ON THE CILIATED GROOVE 
epiblast, the stomodseum ; the portion of it that lies in the region of the mouth, the 
outer portion ; and the portion that communicates with the body-cavity I shall call the 
inner portion; the general cavity of the polyps, which is sometimes short, but some¬ 
times enormously elongated, I shall call the body-cavity ; and in referring to the 
dimorphic forms I shall use the terms “ autozooids ” and “ siphonozooids ” which 
Professor Moseley (15) has introduced in place of the terms “polyps” and “zooids” 
used by Professor Kolliker, and others. 
In Alcyonium palmatum the stomodseum presents in transverse section a rhombic¬ 
shaped cavity, with long lateral walls and short dorso-ventral walls ; it is wide in its 
outer portion, but becomes considerably narrowed towards its opening into the body- 
cavity, so that one might describe it as a funnel which is laterally compressed 
(Plate 50, figs. 1 and 2). 
The ciliated groove, commencing about one-third of the total depth of the stomo¬ 
dseum from the mouth, is continued along its ventral side as far as its opening into the 
body-cavity. 
The stomodseum is lined by a columnar ciliated epithelium, varying in thickness 
from '004 millirn. to *002 millirn. 
The ciliated groove is distinguished by the following peculiarities : the epithelium 
is thicker than it is over the rest of the stomodseum, being at least ‘005 millirn. thick, 
the free edges of the columnar epithelium cells of which it is composed are very clear 
and definite, and the cilia are remarkably long and strong, being from '006 millirn. to 
'007 millirn long. 
Of the genus Alcyonium I have examined three other species, namely, A. digitalum, 
A.pulmonaria, and A. pachydados, but owing to the larger number of spicules in these 
species, they are not so favourable for histological manipulation. 
An examination of living specimens of our English Alcyonium digitatum revealed 
the fact that the cilia of the groove, moving almost simultaneously, produce a current 
of water from without inwards, whereas the cilia lining the rest of the stomodseum 
produce currents in the opposite direction. Thus a complete circulation is brought 
about in tire polyps; the inward current produced by the cilia of the groove is 
probably aided by the cilia of the ventral mesenterial filaments, whilst an outward 
current, commencing on the dorsal and lateral mesenteries, is taken up by the action 
of the cilia lining the general surface of the stomodseum. 
It is evident from anatomical and physical considerations that the chief part of tlie 
propulsion of these currents is performed by the cilia lining the groove on the ventral 
side of the stomodseum, and consequently I propose to call this groove “ the sipho¬ 
noglyphe.” 
I may summarise the characters of the siphonoglyphe in the genus Alcyonium 
as follows :— 
The siphonoglyphe is present along the inner two-thirds of the ventral wall of the 
stomodseum (Plate 50, fig. 2), it is formed by that portion of the wall of the stomodseum 
