. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 72 PAUL A. NICOLL vessels in higher forms. In the few times when cannulation was successful attempts to inject formed material in order to visualize blood flow were dis- appointing. India ink is quickly salted out and precipitated in the walls in the immediate vicinity of its injection. Occasionally a few specks would remain in solution and their progress along the vessels was very helpful in determining flow patterns. RESULTS A. Vascular anatomy Unlike some of the Annelida neither N. virens nor N. limb at a has developed a
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 72 PAUL A. NICOLL vessels in higher forms. In the few times when cannulation was successful attempts to inject formed material in order to visualize blood flow were dis- appointing. India ink is quickly salted out and precipitated in the walls in the immediate vicinity of its injection. Occasionally a few specks would remain in solution and their progress along the vessels was very helpful in determining flow patterns. RESULTS A. Vascular anatomy Unlike some of the Annelida neither N. virens nor N. limb at a has developed a specialized heart or hearts within their vascular system. Although Linville (1907) N .VIRCNS, ANTERIOR END DORSAL VIEW. 1 ,' s9 . C- .' ' ' / i ..-.; oo / <^ ; £ / = jjf^^^ ±^—±:—~. '•"" *i FIGURE 1. Principal vascular elements in anterior segments of Nereis virens. Dorsal view. A, ventral longitudinal vessel; B, dorsal longitudinal vessel; E, recurrent branch—ventral lateral vessel; F, G-I plexus-lateral connective; G, medial branch—ventral lateral vessel; H, stem-ventral-lateral vessel; J, dorsal-lateral vessel. calls the gastro-intestinal branch (vessel F) in each segment a heart, this is hardly justified in the sense that it functions as a force pump. As explained below these vessels appear rather as pace-makers of the segmental system, most vessels of which are also contractile in their own right. Before considering the flow patterns and vascular behavior it is necessary to understand the anatomical relationships that actually exist in these forms. In N. virens the typical reduplicated, segmental vascular pattern is extensively modified in the anterior segments. The vascular organization in this region is an adaptive development to fit the needs of the pharyngeal structures internally and the reduced parapodia externally. No special function within the vascular system itself can be ascribed to these anterior vessels. In a similar sense the segment
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
