ON THE MORPHOLOGY, FEEDING, AND BEHAVIOR OF MAGELONA SP

¹ Division of Worms, Museum of Natural History, Smithsonian Institution, Washington, D. C. 20560

1. Observations were made on the morphology, especially that of the circulatory system, the feeding, and the behavior of the polychaetous annelid Magelona sp. from the vicinity of Woods Hole, Massachusetts.

2. Features of particular interest related to the circulatory system include an anterior dorsal vessel which is divided into a series of chambers set apart by valves. The chambers undergo a precisely timed filling and emptying and pass blood forward to a heavily muscularized portion of the dorsal vessel whose contractions provide the primary pressure for movement of the blood. Segmentally arranged valves were noted in the posterior part of the dorsal vessel.

3. Burrowing is accomplished by the insertion of the prostomium into the substratum and the subsequent extrusion of the proboscis. This extrusion is brought about primarily by the hydraulic pressure of blood which has been expelled from the anterior region of the body by the contraction of all anterior somatic muscles except the proboscidial retractors.

4. Magelona sp. utilizes the papillae of its paired prostomial tentacles in feeding. Food material adheres to distal papillae and is transferred to more proximal papillae when a loop is formed by the tentacle; by repetition of this activity, the food material is passed stepwise toward the mouth.

5. Observations were also made on lateral organs, which may prove to be vibration receptors, and on so-called lateral pouches, whose function is unknown.