. A manual of zoology. Zoology. II. TUNICATA: TETHYOIDEA 445 arranged in longitudinal and transverse rows (fig. 499), through which the water received from the mouth passes into the peribranchial chamber, thence to the atrium, and so to the external world. While the respiratory water thus passes out in a nearly direct course, the food particles which it contains pass into the digestive tract. By means of the peripharyngeal band just inside of the tenta'cles and sur- rounded lay mucus secreted by the endostyle the food is carried back to the cesophagus (oe) at the base of the gill chamber, and
. A manual of zoology. Zoology. II. TUNICATA: TETHYOIDEA 445 arranged in longitudinal and transverse rows (fig. 499), through which the water received from the mouth passes into the peribranchial chamber, thence to the atrium, and so to the external world. While the respiratory water thus passes out in a nearly direct course, the food particles which it contains pass into the digestive tract. By means of the peripharyngeal band just inside of the tenta'cles and sur- rounded lay mucus secreted by the endostyle the food is carried back to the cesophagus (oe) at the base of the gill chamber, and thence to the stomach (usually provided 1 |i (ii=iiJ |j\ ! [ h with liver glands), and on to the intestine. The '' "^ ^ "' anus is at the base of the special portion of the peribranchial chamber, which also receives the genital ducts and hence is known as the cloaca or atrium. In the body cavity, which is greatly reduced in the species with compact bodies, occur the digestive tract, tlie sexual organs, and the -p,„ ,„„ ^. • , ,. f^ ' to ' tlG. 499.—tiona ^ntesip- heart; the latter {he) frequently S-shaped, ex- ?!«/«, a bit of the wall of the tends' between the stomach and the endostyle. g} sUts'"^""'^"^ '° '^'°"'""" Opposite to the endostyle is the ganglion (g) in the dorsal wall between oral and atrial openings. Near it is a branched suhneural gland which has been compared to the vertebrate hypophysis. In many there exist special excretory organs, numerous blind vesicles tilled with excreta. From the eggs are hatched small swimming tadpole-like larvs (fig. 500), resembling Appendictdaria and, like it, consisting of trunk and tail, in which the chordate features are strongly marked. The digestive tract is confined to the trunk; dorsal to it lies the tubular nervous system in which can be recognized a vesicular brain with a simple eye and a statocyst imbedded in its walls; farther back a narrower portion ('medulla o
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectzoology, bookyear1912
