The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . ding the body. The most anterior and posterior of theseform the branchial and atrial sphincters. The wide branchialand atrial apertures lead into large branchial and peribranchial cavi-ties, separated by the posterior wall of the branchial sac, which ispierced by stigmata; consequently there is a free passage for thewater through the body along its long axis, and the animal swims bycontracting its ring-like muscle bands, so as to force out the containedwater posteriorly. Stigmata may al?o be found
The encyclopædia britannica; a dictionary of arts, sciences, literature and general information . ding the body. The most anterior and posterior of theseform the branchial and atrial sphincters. The wide branchialand atrial apertures lead into large branchial and peribranchial cavi-ties, separated by the posterior wall of the branchial sac, which ispierced by stigmata; consequently there is a free passage for thewater through the body along its long axis, and the animal swims bycontracting its ring-like muscle bands, so as to force out the containedwater posteriorly. Stigmata may al?o be found on the lateral walls ofthe branchial sac, and in that case there are corresponding anteriorlydirected diverticula of the peribranchial cavity. There is a distinctendostyle on the ventral edge of the branchial sac and a periphan,n-geal band surrounding its anterior end, but there is no representativeof the dorsal lamina on its dorsal edge. The oesophagus commencesrather on the ventral edge of the posterior end of the branchialsac, and runs backwards to open into the stomach, which is followed. Fig. 20.—Doliolum denltculatum. sexual generation, fromthe left side. Lettering as for fig. —m. Muscle bands. pbr, Peribranchial cavity ng. Nerve ganglion. (Ui, Atrial lobes, sg. Stigmata. so. Sense organs. sgl, Subneural gland. W. Branchial lobes- TUNICATA j^7 by a cuncd intestine opening into the penbranchial cavity. Thealimentary canal as a whole is to the right of the middle line. Thehermaphrodite reproductive organs are to the left of the middle linealongside the alimentary canal. They open into the pcribranchialcavity. The ovary is nearly spherical, while the testis is elongated,and may be continued anteriorily for a long distance. The heartis placed in the middle line ventrally, between the posterior end ofthe endostyle and the oesophageal aperture. The ner\e ganglionlies about the middle of the dorsal edge of the body, and gives offmany nerves. Under it is placed the subn
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectencyclo, bookyear1910
