The Journal of experimental zoology . rm ofchannels (fig. 7) or may be completely lifted. The water passesup between the gills, and escapes under an elevation of the girdleat the posterior end. This elevation is of somewhat variableform, although always located between the posterior ends of theright and left gill series. It is formed as a direct result of thewater current impinging on the inner ventral margin of the girdle. 174 LESLIE B. AREY AND W. J. CROZIER Figure 8 illustrates this point. When a chiton, partially out ofwater, on the wall of an aquarium, swings from a vertical posi-tion (fi
The Journal of experimental zoology . rm ofchannels (fig. 7) or may be completely lifted. The water passesup between the gills, and escapes under an elevation of the girdleat the posterior end. This elevation is of somewhat variableform, although always located between the posterior ends of theright and left gill series. It is formed as a direct result of thewater current impinging on the inner ventral margin of the girdle. 174 LESLIE B. AREY AND W. J. CROZIER Figure 8 illustrates this point. When a chiton, partially out ofwater, on the wall of an aquarium, swings from a vertical posi-tion (fig. 7) to one such as that shown in figure 8, the posterior,elevated part of the girdle travels to one side as a smooth water current also enables a chiton to sample the surround-ing water. It is of importance for reproduction, since the stim-ulus to egg laying is provided by the diffusion of sperm fromnear-by males; these sperms are carried past the openings of theoviducts, past the osphradia (p. 253), and eggs are liberated. / 7 8 Fig. 7 Illustrating the course of the water current n Chiton. Diagram-matic. Fig. 8 The course of the water current in Chiton when the animal is par-tialiy submerged. Diagrammatic. in their company (Metcalf, 92; Heath, 99, 05 c). The ne-phridia also discharge their excretions into the respiratory cur-rent. These excretions, together with the water that has beenused, are usually shot to a considerable distance, because, theanal opening being smaller than the incurrent openings, thevelocity of the outgoing current is high; here also, as in Ascidia(Hecht, 18), the used water is discharged in such a way thatit is not readily employed again for breathing purposes. The ventral surface of the girdle is transversely ribbed, pro-viding minute channels through which water is taken in, even THE SENSORY RESPONSES OF CHITON 175 when the girdle is not detectably lifted; this can be demonstratedwith suspended carmine. The girdle can, however, be verytightl
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