Text-book of comparative anatomy . ture from thegeneral plan of the principal vesselsin the pharyngeal region is evidentlycaused by the great development ofthe pharynx. If they lay as close toFIG. 167.—Part of a transverse section through the pharynx as they do to the intes-a segment of the body of Nephthys, diagrammatic, tine in the rest of the body) they to demonstrate the arrangement of the blood-vessels , •, , , , •, ., would be broken by its protrusion,(partly after Jaquet). dp, Dorsal; vp, ventral para- J l pdium, with bundles of sete and supporting seta; vd, The ventral vessel gives ris
Text-book of comparative anatomy . ture from thegeneral plan of the principal vesselsin the pharyngeal region is evidentlycaused by the great development ofthe pharynx. If they lay as close toFIG. 167.—Part of a transverse section through the pharynx as they do to the intes-a segment of the body of Nephthys, diagrammatic, tine in the rest of the body) they to demonstrate the arrangement of the blood-vessels , •, , , , •, ., would be broken by its protrusion,(partly after Jaquet). dp, Dorsal; vp, ventral para- J l pdium, with bundles of sete and supporting seta; vd, The ventral vessel gives rise in eachdorsal vessel; vv, ventral vessel; gin, lateral vessels segment to a pair of lateral vessels,of the ventral chord; vg, connecting vessel between AVhich run along to the base of thethe dorsal and ventral parapodia; a, intestine; Im, ventral branclles Of the parapodia,ventral chord ; k, gills ; kr/, branchial vessels. ... passing into the latter and there rami- the lateral branches of the dorsal vessel and the. fying. A connection betweenlateral branches of the ventral vessel takes place in the following way. Betweenthe dorsal and ventral branches of a parapodium there runs on each side a vesselwhich ramifies on one side in the dorsal branch, on the other in the ventral ramifications of the connecting vessels anastomose with the ramifications ofthe dorsal or ventral lateral vessels. On the ventral side of each dorsal parapodialbranch a sickle-shaped gill is inserted. Two vessels from the vascular system of thedorsal parapodial branch enter the gill, and with many windings and anastomosesrun through its whole length. Besides the dorsal and ventral vessels, Nephthyspossesses also two extremely delicate lateral vessels of the ventral chord, which areconnected by fine branches with the lateral branches of the ventral vessel. This arrangement of the blood-vascular system can, however, only to a very limitedextent be considered typical of the Polychccta. In
Size: 1530px × 1633px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
