. The biology of marine animals. Marine animals; Physiology, Comparative. 430 THE BIOLOGY OF MARINE ANIMALS Removal of the radial nerve cord abolishes longitudinal conduction and co-ordinated locomotory responses in the arm. The movements of the tube feet are regulated by five centres, each of which lies at the junction of the circumoral ring with a radial nerve (Fig. ). From each centre fibres enter the contiguous radial nerve, and also proceed in both directions Mot. A. Fig. Schematic Diagram of Nerve Centres and Tracts Involved in the Innervation of the Tube Feet of Starfish I-V,
. The biology of marine animals. Marine animals; Physiology, Comparative. 430 THE BIOLOGY OF MARINE ANIMALS Removal of the radial nerve cord abolishes longitudinal conduction and co-ordinated locomotory responses in the arm. The movements of the tube feet are regulated by five centres, each of which lies at the junction of the circumoral ring with a radial nerve (Fig. ). From each centre fibres enter the contiguous radial nerve, and also proceed in both directions Mot. A. Fig. Schematic Diagram of Nerve Centres and Tracts Involved in the Innervation of the Tube Feet of Starfish I-V, radial cords of arms I-V; centre I, one of the five nerve centres of the circumoral ring; Mot. A, Mot. C, motor neurones of the first and second orders, respectively; m, segment of the tube foot musculature; , nerve ring; , tube foot. Motor neurones of the first order (Mot. A) lie in the radial perihaemal canal and their axons invade the tube foot, where they make synaptic connexion with second-order motor neurones (Mot. C); the latter supply the postural muscles of the foot. (From Smith (103).) around the ring to the other arms. During normal locomotion of a starfish one of these centres becomes dominant, co-ordinates the direction of stepping movements in all arms and causes the animal to move in one particular direction. A similar innervation pattern has been discovered in the circumoral ring and radial nerves of sea cucumbers (Cucumaria), where the responses. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Nicol, J. A. Colin (Joseph Arthur Colin), 1915-. New York, Interscience Publishers
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