The distinction, therefore, between the movement of the eyeballs, elicited from the occipital (visual) cortex, and that of the hand, elicited from the cortex in the region of the central sulcus (somaesthetic), is not a difference between motor and sensory, for both are sensori-motor in the nature of their reactions; the difference is only a difference between the kind of sense and sense-organ in the two cases, the muscular apparatus in each case being an appanage of the sensual.
These grooves are known as the sulcus and sulculus, and will be more particularly described hereafter.
There is only one ciliated groove, the sulcus, in the stomodaeum.
In these the tentacles are stunted or suppressed and the mesenteries are ill-developed, but the sulcus is unusually large and has long cilia.
Mm, Mesenteries; budding from a single mb muscle banners; sc, sulcus; st, parent zooid.
The stomodaeum is compressed laterally, and is furnished with two longitudinal grooves, a sulcus and a sulculus.
S, Sulcus; sl, sulculus.
The third pair is formed in the sulcar chamber, in close connexion with the sulcus, and in this case the muscle-banners are on the sulcular faces.
Externally they resemble ordinary sea-anemones, but there is only one ciliated groove, the sulcus, in the stomodaeum, and the mesenteries are arranged on a peculiar pattern.
Each zooid has six tentacles; the stomodaeum is elongate, but the sulcus and sulculus are very feebly represented.
Each mesentery has a filament; but two of them, namely, the pair farthest from the sulcus, are longer than the rest, and have a different form of filament.
The arrangement of the muscle-banners on the mesenteries is characteristic. On six of the mesenteries the muscle-banners have the same position as in the Alcyonaria, namely, on the sulcar faces; but in the two remaining mesenteries, namely, those which are attached on either side of the sulcus, the muscle-banners are on the opposite or sulcular faces.