. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 2S4 of the stomach and the circular vessel, which is formed from the dorsal tube. They are at first enclosed in a cavity, from, which later on they penetrate to the exterior. The larva retracts its lateral lobes and transforms itself into a barrel- shaped body with five transverse rows of cilia, and loses the mouth and dorsal pore (fig. 229). The ambulacra! system gradually de- velops further, the intestine be- comes longer, the first five tentacles break through to the exte
. Elementary text-book of zoology, tr. and ed. by Adam Sedgwick, with the assistance of F. G. Heathcote. 2S4 of the stomach and the circular vessel, which is formed from the dorsal tube. They are at first enclosed in a cavity, from, which later on they penetrate to the exterior. The larva retracts its lateral lobes and transforms itself into a barrel- shaped body with five transverse rows of cilia, and loses the mouth and dorsal pore (fig. 229). The ambulacra! system gradually de- velops further, the intestine be- comes longer, the first five tentacles break through to the exterior, the mouth appears at the anterior pole, and the first suctorial foot with its ambulacra! vessel is seen on the ventral surface (fig. 230). The animal gradually loses the bands of cilia, and as a young Ilolothurian creeps about by means of its ten- tacles and of the first ambulacral foot, which is soon followed by a second new one. In the more direct development the bilateral larva seems to be more or less completely suppressed, and the time of free-swimming life shortened or altogether dispensed with. In these cases, protective arrangements, such as brood pouches, are always present in the mother. The brood pouch of Pterastcr militaris is the most carefully pro- tected. It lies above the anus and generative open- ings ; its walls are highly charged with calcareous FIG. 229.—Auricularia pupa of Synapta seen in profile (after E. Metschnikoff). The mouth is already large, so that the tentacles (T) can be protruded. TfV, Ring of cilia; Pe, Pi, somatic visceral layers of the peritoneal sacs; Ob, auditory vesicle; Po, pore of the water-vascular system; It, cal. cureous wheel-shaped 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 Claus, Carl, 1835-1899; Sedgwick, Adam, 1854-1913; Sinclair, F. G.
Size: 1355px × 1844px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., book, bookcentury1800, bookcollectionbiodiversity, bookdecade1890
