. The Biological bulletin. Biology; Zoology; Marine biology. 266 SHOU-HWA CHUANG shell valves and was almost filled with the stomach and the intestine (Fig. 1). A cone of tissue projected laterally from the lateral body wall at the level of the stom- ach. This setal cone contained the bases of the long straight, brittle setae, which will be referred to as the embryonic setae in the present study. This cone also housed the muscles to move these setae. The rest of the space bet\\'een the shell Aahes not occupied by the visceral cavity constituted the mantle cavity. In the front part of this was
. The Biological bulletin. Biology; Zoology; Marine biology. 266 SHOU-HWA CHUANG shell valves and was almost filled with the stomach and the intestine (Fig. 1). A cone of tissue projected laterally from the lateral body wall at the level of the stom- ach. This setal cone contained the bases of the long straight, brittle setae, which will be referred to as the embryonic setae in the present study. This cone also housed the muscles to move these setae. The rest of the space bet\\'een the shell Aahes not occupied by the visceral cavity constituted the mantle cavity. In the front part of this was a contractile columnar projection of the anterior body wall. This column contained the oesophagus,. 50AI Figure 1. Ventral view of a young discinid larva (no. 15, Table) with embryonic setae (1-3) and a curved seta issuing from each setal cone. The stomach (S) and intestine (I) almost fill up the visceral cavity. pharynx and muscles and continued anteriorly into the lophophore. Muscular movements of the column and lophophore brought about extension and expansion or retraction and contraction of both column and lophophore. The larval lophophore consisted of a central disk roughly horizontal in position with the more or less centrally placed mouth on the ventral side. At the periphery of the disk 9 lophophoral processes radiated out. One of these, the tentacle, pointed anteriorly in the sagittal plane, and the others, the cirri, were more lateral in posi- tion. All the larvae in the present series had 4 pairs of cirri. Each cirrus on one side of the mouth usually corresponded in position and size with the one directly opposite on the other side, thus forming a pair. A thin layer of mantle tissue lined the inner surface of the mantle cavity. In widely separated regions along the lateral border of the ventral mantle typically 4 stout curved setae appeared on each side of the medium-sized larvae. From each. Please note that these images are extracted from scanned page images that ma
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectb, booksubjectzoology
