. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 128 WESLEY R. COE. just behind the head. In Neuronemertes the walls of the sper- maries are not provided with the thick spiral musculature found in several other pelagic forms and which serves to supplement the weak muscles of the body walls in the forcible discharge of the spermatozoa. A similar result is accomplished however by the contraction of the highly developed dorsoventral muscles which closely invest the spermaries in that genus. It therefore seems reasonable to suspect that these supplementary nervous tissues may
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 128 WESLEY R. COE. just behind the head. In Neuronemertes the walls of the sper- maries are not provided with the thick spiral musculature found in several other pelagic forms and which serves to supplement the weak muscles of the body walls in the forcible discharge of the spermatozoa. A similar result is accomplished however by the contraction of the highly developed dorsoventral muscles which closely invest the spermaries in that genus. It therefore seems reasonable to suspect that these supplementary nervous tissues may function in the control of this dorsoventral muscu- lature throughout the body. There still remains the possibility of the ganglia being corre- lated with sensory stimuli rather than with motor responses, but their structure is unlike that of any known receptor. It seems necessary, therefore, to return to the view that the ganglia of the dorsal nerve supplement the nerve cells of the lateral nerve cords just as these supplement those of the FIG. 5. Transverse section of lateral nerve cord in three different genera, showing the relations of the fibrous cores to the accompanying nerve cells. A, Plionemertcs plana Coe, with single fibrous core (fc) and symmetrical dorsal and ventral cellular layers (del and vcl) ; B, Proarmaueria pellucida Coe, with small dorsal core (fcr) ; C, Planoncmcrtcs lobata Coe, with large dorsal core. Lateral nerves.—These are direct continuations of the fibrous cores of the brain lobes and are accompanied by nerve cells throughout their entire length. At the posterior end of the body the cords of the two sides form a broad commissure on the dorsal side of the rectum (Fig. i). In most pelagic species the fibrous core arising from the dorsal brain lobe is separated by a layer of ganglion cells, at least in the anterior part of the body, from that arising from the ventral lobe of the brain (Fig. 5).. Please note that these images are extracted fro
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
