. Outlines of zoology. Zoology. NEMERTEA. 177 approximations tend towards the two positions most characteristic of the nervous systems of Annelids and Arthropods on the one hand, and of Vertebrates on the other. Lateral 0?-gans. On each side of the head there is a ciHated pit communi- cating with the exterior through an open sht or groove, and communicating internally either with the brain itself, or with adjacent and associated nervous tissue. In those cases in which the development has been studied these so-called d. Fig. 57.—Transverse section of the Nemertean Drepanophonis latus. (Af
. Outlines of zoology. Zoology. NEMERTEA. 177 approximations tend towards the two positions most characteristic of the nervous systems of Annelids and Arthropods on the one hand, and of Vertebrates on the other. Lateral 0?-gans. On each side of the head there is a ciHated pit communi- cating with the exterior through an open sht or groove, and communicating internally either with the brain itself, or with adjacent and associated nervous tissue. In those cases in which the development has been studied these so-called d. Fig. 57.—Transverse section of the Nemertean Drepanophonis latus. (After BiJRGER.) (/.«., Dorsal nerve ; ^ proboscis sheath ; Px., proboscis cavity ; \ sac of proboscis cavity; , dorso-ventral muscles ; , circular muscles ; /.;«., longitudinal muscles ; , lateral nerve with branches ; /"., parenchyma ; ,jr., gut ; /.z'., lateral blood vessel, beside which excretory vessel; -£./-, excretory pore; '.\ dorsal blood vessel; -£"/., epidermis. lateral organs arise from epiblastic insinkings and oesophageal outgrowths. In the most primitive genus, Carinelia, they are absent, except in one species. It has been suggested that they conduce to the respiration of the brain, which is rich in haemoglobin, and they have even been compared with gill slits. In some forms the groove through which they 12. 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 Thomson, J. Arthur (John Arthur), 1861-1933; Newbigin, Marion I. (Marion Isabel), 1869-1934; Smith, Preserved, 1880-1941. fmo. New York, D. Appleton & Co.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
