. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 296 DIANA VALIELA WARD contractions must occur at most hinge joints whose muscles are not direct effectors of the movements being performed in walking. The last pair of legs (prosomal appendages VI) has so far been excluded from the above descriptions because of its special movements. Even when these legs are off the ground, they may perform up to 120 degrees of extension of the femoro- patellar joints, provided the legs are positioned almost horizontally (see Fig. 7). The legs are kicked backwards, resulting in a straight-l
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 296 DIANA VALIELA WARD contractions must occur at most hinge joints whose muscles are not direct effectors of the movements being performed in walking. The last pair of legs (prosomal appendages VI) has so far been excluded from the above descriptions because of its special movements. Even when these legs are off the ground, they may perform up to 120 degrees of extension of the femoro- patellar joints, provided the legs are positioned almost horizontally (see Fig. 7). The legs are kicked backwards, resulting in a straight-line configuration of all the segments in the legs. This results in a nearly ISO-degree angle at the extensorless femoro-patellar joint, or a total extension of 120 degrees from the flexed position for most sixth legs. The same movement occurs when the animal is FIGURE 6. Extension of left leg V (anterior view) when the animal is in the normal upright position. The only muscles shown are those thought to effect the extension of the hinge joint. a: leg elevated, b: leg depressed and extended. T = trochanter, F = femur, P = patella. The backwards rotation of the coxa is doubtless due to the coxal remoter muscles. Since the leg is now in a horizontal position, the axes of the joints are in a vertical position; therefore the weight of the segments beyond the femoro-patellar joint does not tend to flex that joint. The other pairs of legs also have coxal remoter muscles; however, the motions just described are not performed to any significant extent because rotation of the coxa is limited by the closely following coxae of more poste- rior legs. Note the position of the coxa of leg V in Figure 7b(ii). The last pair of legs are the legs which seem to do most of the work in pro- pelling the animal through mud and sand by rapid straightenings and application of the large area of their distal flattened spines to the substrate. The locomotion of Limulns through mud or on dry g
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
