. Outlines of zoology. Zoology. GENERAL ACCOUNT OF NEMERTEA. 171 systems of Annelids and Arthropods on the one hand, and of Verte- brates on the other. On each side of the head there is a ciliated pit communi- cating with the exterior through an open slit or groove, and communicating internally either with the brain itself or with adjacent nervous tissue. In those cases in which the development has been studied, these so-called lateral organs d. v. Fig. 76.—Transverse section of the Nemertean Drepanophorus latus. —After Burger. Dorsal or proboscis nerve; , proboscis sheath; P
. Outlines of zoology. Zoology. GENERAL ACCOUNT OF NEMERTEA. 171 systems of Annelids and Arthropods on the one hand, and of Verte- brates on the other. On each side of the head there is a ciliated pit communi- cating with the exterior through an open slit or groove, and communicating internally either with the brain itself or with adjacent nervous tissue. In those cases in which the development has been studied, these so-called lateral organs d. v. Fig. 76.—Transverse section of the Nemertean Drepanophorus latus. —After Burger. Dorsal or proboscis nerve; , proboscis sheath; , proboscis cavity; '., sac of proboscis cavity; , dorso-ventral muscles; cm., circular muscles; /.;//., longitudinal muscles; /.«., lateral nerve with branches; P., parenchyma; g., gut; Lv., lateral blood vessel, beside which lies an excretory vessel; , excretory pore ; , dorsal blood vessel ; Ep., epidermis. arise from epiblastic insinkings and oesophageal outgrowths. In the most primitive genus, Carinella, 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 open to the exterior is rhythmically contractile. It has also been suggested that they are sensory. Apart from these organs, Nemertines are very sensitive, and in many this is associated. 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. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
