. Bulletin - United States National Museum. Science. ^sim an. Fig. 142.—Apsteinia astmmeteica, soli- tary form. Ventral view of the oesophagus, stomach, and intes- tines from an individual 18 mm. long, showing adult character. of the upper lip. Muscle 5 of the upper lip is a branch of the inter- mediate muscle. Muscle 1 of the upper lip lies at its incurved edge. Posteriorly it is in contact with the dorsal retractor muscle and functions with it, though the fibers of the two muscles are not continuous. Muscles 2 and 3 of the upper lip are continuous, respectively, with muscles 3 and 4 of the l
. Bulletin - United States National Museum. Science. ^sim an. Fig. 142.—Apsteinia astmmeteica, soli- tary form. Ventral view of the oesophagus, stomach, and intes- tines from an individual 18 mm. long, showing adult character. of the upper lip. Muscle 5 of the upper lip is a branch of the inter- mediate muscle. Muscle 1 of the upper lip lies at its incurved edge. Posteriorly it is in contact with the dorsal retractor muscle and functions with it, though the fibers of the two muscles are not continuous. Muscles 2 and 3 of the upper lip are continuous, respectively, with muscles 3 and 4 of the lower lip and are not connected with either oral retractor muscle. The little blunt protuberance in figure 140, in the angle between the intermediate muscle and the fifth sphincter of the upper lip, is not a muscle, but a blood vessel. The atrial muscles (figs. 140 and 141) form a graduated series, as in Apsteinia punctata (figs. 49 and 52, pp. 72 and 74), and show a similar atrial retractor. Over body muscle IX, on each side, in the embryo, is a small, very short epithelial tube with collapsed, but not open, end. It is indicated by a question mark on figures 140 and 141. The function of these structures is doubtful, but one suspects they may serve as aids in attaching the embryo to its nurse. These organs are not present in our adult specimens. The much longer pos- tero-lateral languets, shown by Apstein in the embryo of this species which he fig- ures (fig. 58, p. 78), are probably the same structure. The placenta and eleoblast are in the usual condition. The gut in the em- bryo forms an open loop around the intestinal gland. In the adult the gut is more compact (fig. 142), really forming a so-called intestinal nucleus, though the elongated character of the stomach makes this "nucleus" less spherical than in the true B. Fig. 143.—Apstenia asymmetrica. Dorsal views: A of the cili- ated FUNNEL AND ANTERIOR END OF THE GILL OF AN ADULT SOLI- TARY INDIVIDUAL
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