Each palpacle is a tactile filament, very extensile, without accessory filaments or nematocysts.
Denoting the cross-section a of a filament by dS and its mass by dm, the quantity wdS/dm is called the vorticity; this is the same at all points of a filament, and it does not change during the motion; and the vorticity is given by w cos edS/dm, if dS is the oblique section of which the normal makes an angle e with the filament, while the aggregate vorticity of a mass M inside a surface S is M - l fw cos edS.
Cephalic shield continuous with neck; twelve to fourteen stomachal plates; a posterior pallial filament passing through a notch in shell.
In short, the little chisel becomes in his fingers a painters brush, and when it is remembered that, the basis upon which he works being simply a thread of silk, his hand must be trained to such delicacy of muscular effort as to be capable of arresting the edge of the knile at varying depths within the diameter of the tiny filament, the difficulty of the achievement will be understood.
Tungsten has been applied in the manufacture of filament electric lamps.