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Abstract

STUDIES with the light microscope1–4 have produced a picture of the sensory element of the statocyst of decapod Crustacea, the innervation of which had not previously been understood. A typical hair of the crescent group of the cyst consists of a long shaft with a base that is shaped like a cask. One part of the wall of the cask is reinforced by sclerotized layers which form the “tooth”, the rest of the wall is membraneous1,2 (Fig. 1). Opposite the tooth a light-refractive thread, the chorda1,2, enters a cuticular spine of the shaft—the lingula. The chorda, composed of chitinous material2, seems to originate close to the sense cells. Hensen1 has described the chorda as the terminal fibre of the nerve, ending in the cask. Prentiss3 also thought the nerves ended in the cask. Kinzig2, on the other hand, suspected that the chorda runs inside the nerve fibre as a stiffening element, and vom Rath4 recorded that the nerve terminated in the tip of the hair. He found several sense cells connected to one hair4; other investigators observed a one to one relationship2,3.