Text-book of comparative anatomy . into a muscular, spherical, oregg-shaped oesophageal bulb (pharynx). Between the mid-gut (stomach) VI TARDIGRADA 545 and the cesophageal bulb an oesophagus is intercalated. Two blindtubes enter the rectum, no doubt corresponding with the Malpighianvessels of the Tntcliciita. The sexes are separate ; the germ glands unpaired, and sac-shaped. In both sexes they enter the hind-gut, which thus becomesa cloaca. Special circulatory and respiratory organs are nervous system consists of a brain, an infra-cesophageal gan-glion which is connected with the b
Text-book of comparative anatomy . into a muscular, spherical, oregg-shaped oesophageal bulb (pharynx). Between the mid-gut (stomach) VI TARDIGRADA 545 and the cesophageal bulb an oesophagus is intercalated. Two blindtubes enter the rectum, no doubt corresponding with the Malpighianvessels of the Tntcliciita. The sexes are separate ; the germ glands unpaired, and sac-shaped. In both sexes they enter the hind-gut, which thus becomesa cloaca. Special circulatory and respiratory organs are nervous system consists of a brain, an infra-cesophageal gan-glion which is connected with the brain by two cesophageal commis-sures, and 4 other ventral ganglia, which are connected by longitudi-nal commissures placed far apart from one another. There are twoeye spots in the head, lying on twosmall ganglia connected by nerves withthe brain. The musculature is richlydeveloped. Various dorsal, ventral,and lateral longitudinal muscles rununder the integument. Special musclesserve for moving the legs. All themuscles are Fig. 3S3. — Posterior portion of thebody of Macrobiotus Hufelandii £ , fromthe side, h, Testis ; ad, accessory gland ofthe male sexual apparatus ; cl, cloaca ; an,anus; vm, excretory tube (Malpighianvessel); md, mid-gut (after Plate). The systematic position of the Tardigrada Y\ll;^-^r /--ad is uncertain. The three related facts thatthey possess accessory organs of the hind-gutcomparable with the Malpighian vessels, tube-like oral glands, and truncated feet providedwith claws, make it not improbable thatthey belong to the Arthropoda, and especiallyto the Tracheata. The want of oral limbs,the structure of the nervous system, and themanner of emergence of the sexual organs,stand in the way of a comparison of the Tar-digrada with the Acarina. Although wemay agree with the view that they are some-how related to the Tracheata, or to the ances-tors of the Tracheata, we cannot in any case assume that they, in any way, resemblethe primitive arrangements.
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectanatomycomparative
