The dorsal vessel is an elongate tube, Oblique tergal whose abdominal portion is usually c ha m b e r e d, forming a contractile heartfi Io the (g io).) At th ' constrictions between the pericardium l?': ?:' chambers are paired slits, through which the blood passes from the surround Tergo-sternal . [Please select]
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Disjunct: with head, thorax and abdomen separated by constrictions. [Please select]
The topmost of these disks falls off and dies; but all the others separate by the deepening of the constrictions, and swim off as little free disks (Fig.) [Please select]
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