. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. c. FIGURE 3. (a) The initial movement following posterior stimulation with an anterior cut. (b) Normal avoidance response to an anterior stimulus, (c) Avoidance response to an anterior stimulus after an anterior cut. Drawings were made from life. opposite sides of the animal and across the midline so that both longitudinal nerve cords were severed. The contraction pattern is typical of ditaxic locomotion. Ditaxic locomotion can be elicited when three interdigitating cuts are made (Fig. 2b) but movement could not be evok
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. c. FIGURE 3. (a) The initial movement following posterior stimulation with an anterior cut. (b) Normal avoidance response to an anterior stimulus, (c) Avoidance response to an anterior stimulus after an anterior cut. Drawings were made from life. opposite sides of the animal and across the midline so that both longitudinal nerve cords were severed. The contraction pattern is typical of ditaxic locomotion. Ditaxic locomotion can be elicited when three interdigitating cuts are made (Fig. 2b) but movement could not be evoked in all preparations. Conduction did not occur around more than three overlapping cuts. An interesting situation occurs when a cut is made behind the brain and continued posteriorly along the midline for most of the animal's length (Fig. 2c). Stimulation of the anterior portion of this strip results in ditaxic locomotion at the anterior end of the animal. Therefore the information is conducted posteriorly before being conducted anteriorly to the brain. Lesions anterior to the brain When a cut is made from the antero-lateral margin to a point midway in front of the brain (Fig. 3a), animals prodded behind the brain move ditaxically. How- ever, the flap of anterior margin produced by the cut, does not take part in the process. The uncut portion performs normally but on the lesioned side muscular extension only occurs behind the cut. Movement waves are propagated posteriorly from this point. If an intact animal is prodded along the anterior margin it twists to the opposite side before moving away (Fig. 3b). A cut made between the brain and the anterior stimulus site results in a different kind of reaction (Fig. 3c). The animal no longer performs the twisting avoidance reaction but retracts and backs away. DISCUSSION The major finding of this study is the presence of an apparent sensory nerve-net in Notoplana, a turbellarian. This system resembles those classically designated as n
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
