. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 300 ANNELIDA. fact, as well as the formation of the prteoral lobe and the develop- ment of the ventral hooked setre, points to a close relationship with the Clicetopoda. In the adult animal, however, the internal segmen- tation is very little marked. The dissepiments, with the exception of the first, which forms a partition between the head and the body, are lost, and the segmentation of the ventral cord is only indicated by the distribution of the nerves. The supra-oesophageal ganglion rem
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 300 ANNELIDA. fact, as well as the formation of the prteoral lobe and the develop- ment of the ventral hooked setre, points to a close relationship with the Clicetopoda. In the adult animal, however, the internal segmen- tation is very little marked. The dissepiments, with the exception of the first, which forms a partition between the head and the body, are lost, and the segmentation of the ventral cord is only indicated by the distribution of the nerves. The supra-oesophageal ganglion remains at the apical region of the prseoral lobe (proboscis); hence the cesof hageal commissures are extraordinarily long. The strongly developed prseoral lobe forms a proboscisrlike. FIG. 314.—a, female of Bonfllia riridu (after Lacnzc-Duthiers). I, Integument and generative organs after the intestine has been removed. Hd, Cutaneous glands ; Ab, anal vesicle ; Ad, rectum ; OP, ovary ; Tr, ciliated funnel of the uterus (17). c, Anatomy of iV/< /'/ n tiridis (after Lacaze-Duthiers). D, alimentary canal with anal vesicles (Al) ; M, mesen- tery ; U, uterus; R, proboscis. appendage which may develop to a considerable length and become forked (Bonellia} (fig. 314 a). A pair of hooked seta? (with reserve seta? in the sheath of each seta) are always present on the first segment of the body. In Echiurus there are also one or two circles of set»3 at the posterior end of the body. There are from one to three pairs of anterior segmental organs (so-called brown tubes or ventral glands), which open on the ventral surface and are used for the passage outwards of the generative products. Besides these there is also a pair of. 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 Claus, Carl, 1835-1899; Sedgwick, Adam, 1854-1
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