. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLYDORA COMMENSALIS 363 segments have both dorsal and ventral cirri with the exception of the fifth. The ventral cirri are hetter developed (Fig. 5). Ciliated swellings lateral to the vestibule become very apparent by the 12-setiger stage. These lateral lips continue to enlarge and in advanced larvae appear enor- mous when the mouth is wide open. A prototroch runs across the ventral side of the lateral lips to either edge of the vestibule. It reaches the dorso-lateral edge of the lateral lips, but does not extend across the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. POLYDORA COMMENSALIS 363 segments have both dorsal and ventral cirri with the exception of the fifth. The ventral cirri are hetter developed (Fig. 5). Ciliated swellings lateral to the vestibule become very apparent by the 12-setiger stage. These lateral lips continue to enlarge and in advanced larvae appear enor- mous when the mouth is wide open. A prototroch runs across the ventral side of the lateral lips to either edge of the vestibule. It reaches the dorso-lateral edge of the lateral lips, but does not extend across the dorsal side. A minute prototroch is still observed as late as the 28- segment stage. The telotroch extends across the ventral side in patches. All larval stages exhibit a large dorsal gap. Neither a neurotroch nor ciliated pit has Posterior end of a 25-segment P. commensalis larva. Dorsal view ; nototrorhs omitted. been observed at any stage. Prominent gastrotrochs are present in six to eight patches on segments 3, 5, 7, 10, 13, 15, 17, 19, 21, 23, 25, etc. Nototrochs are present in eight patches across the dorsum. The most lateral patch on each side is composed of "grasping cilia" (Wilson, 1928). Usually, nototrochs begin on segment 3 and are present on every segment thereafter. Occasionally, however, a small nototroch is present on segment 2. Between the 9- and 10-setiger stage, small swellings, palpi anlage, are observed posterior to the prototroch and anterior to the first segment. These buds gradually increase in length, but remain rather small in relation to the body size, even in the oldest larval stages (Fig. 4). They are greatly reduced compared to other spionid 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 Marine Biological Laboratory (Woods Hole, Mass. ); Marine Biolog
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Keywords: ., bookauthorlilliefrankrat, booksubjectbiology, booksubjectzoology
