A NEW HISTOLOGICAL REGION IN HYDRA OLIGACTIS PALLAS

We have observed that the basal disc's ectoderm in hydra not only secretes adhesive material, with which the polyp fixes itself to some submerged surface, but that it also under certain conditions elaborates a gas. This gas is caught within the mucus-like secretion of the basal disc and retained therein. The bubble, thus retained, increases in size until the hydra is lifted to the surface by it. At the surface of the water the retaining vesicle of mucus breaks and spreads as a circular raft from which the hydra hangs beneath the water's surface.The ectoderm of the basal disc is thus seen to have a double function. Associated with this region of the ectoderm of hydra there has been found a pecular region of endoderm. The endoderm of this region is characterized by its component cells having the appearance of the epithelio-muscular cells of the oral two thirds of the body as over against the highly vacuolated epitheliomuscular cells of the aboral third of the body.