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.