Text-book of comparative anatomy . the parapodia are entirely obliter-ated, no doubt in adaptation to thetubicolous manner of life. They are also wanting in the Archiannelida. We donot always find separate ventral anddorsal parapodia ; there is often on eachside only one row of parapodia. Wethen, however, find in each parapodiuma dorsal and a ventral branch. Whetherthe uniserial or the biserial arrangementis the original cannot yet be decided. In the Polychceta the parapodia them-selves again carry characteristic append-. ac FIO. Eunice iimosa (after ages (Fig. 124). These are the eirri,
Text-book of comparative anatomy . the parapodia are entirely obliter-ated, no doubt in adaptation to thetubicolous manner of life. They are also wanting in the Archiannelida. We donot always find separate ventral anddorsal parapodia ; there is often on eachside only one row of parapodia. Wethen, however, find in each parapodiuma dorsal and a ventral branch. Whetherthe uniserial or the biserial arrangementis the original cannot yet be decided. In the Polychceta the parapodia them-selves again carry characteristic append-. ac FIO. Eunice iimosa (after ages (Fig. 124). These are the eirri,Ehiers). Anterior and posterior ends uiisegmented or segmented filaments, one of the body; dorsal side, fa, Unpaired Q£ ^j^ jn the simplest cases, OCCUrS Oilfeeler ; fp, paired feelers ; a, eyes ; fc, ,. ,„ , •,• feeler-cirri ; fc, gills ; pe, dorsal para- each parapodium. We can _ thus CilS- podiai cirri; p, parapodia; ac, anal tinguish dorsal and ventral cirri. Thecirri- cirri may undergo the most varied trans- formations. Thus the dorsal cirri, or their lateral branches, frequentlybecome gills, which are often delicately branched and provided with iv VERMES—FOEM OF BODY AND ORGANISATION 189 « blood-vessels. In the Aphroditidce they become broad dorsal scales(elytra). In some cases ( Ca/pitettidce, Glyceridce) the dorsal para-podia may carry, besides the typical cirrus or the cirrus transformedinto a lateral organ, a gill, Avhich, in contradistinction to the gill whicharises from the cirrus, is cal
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
