. The Bible and science. lso we have a true vascularsystem containing blood. The nervous system consists,in its typical form, of two cords running along thewhole length of the belly, and having a nervous swell-ing or ganglion in each segment. The first pair ofganglia is situated above the gullet, so that thenervous cords, descending to join the second pair,encircle the gullet with a ring or collar. The presenceor absence of limbs furnishes a distinction by whichthe annulosa are divided into two branches—anar-thropoda, where limbs are absent, and arthropodaor articulata, in which limbs are pres
. The Bible and science. lso we have a true vascularsystem containing blood. The nervous system consists,in its typical form, of two cords running along thewhole length of the belly, and having a nervous swell-ing or ganglion in each segment. The first pair ofganglia is situated above the gullet, so that thenervous cords, descending to join the second pair,encircle the gullet with a ring or collar. The presenceor absence of limbs furnishes a distinction by whichthe annulosa are divided into two branches—anar-thropoda, where limbs are absent, and arthropodaor articulata, in which limbs are present. To theformer belong leeches, earthworms, and the lobworm RESPIRATION-GENERAL SKETCH. 14 It of our coasts, while the latter consist of crabs, spiders,centipedes, and insects. The lobsters and crabs are all adapted for life in thewater, and they breathe by means of gills. Here we have a much more complicated arrange-ment for the conveyance of oxygen to the tissues of thebody than in any of the classes yet F:g. 73.—Nervous system of insects, b, of a beetle, c, of a fly. In the simple protista, such as the monera, all partsof the creatures body could obtain oxygen from the sut-rounding medium; in the protozoa, such as the amoeba,we had a provision for driving the nutritive juices ofthe animal throughout its protoplasmic substance by 150 RESPIRATION—USE OF BLOOD. means of a vacuole ; in the hydra and sea-anemone itwas supplied by the sea-water which bathed both theexternal surface of the animal and the interior of itsbody cavity; in the annuloida it was carried by thewater vascular system which communicated with thewater in which the animal swims; but in the annu-losa we have something quite new. In them wefind true blood, a fluid which carries oxygen to thetissues in order to keep up combustion and maintainfunctional activity, and at the same time conveys tothem nutriment, to supply the waste which occurs inthe process. The muscles in the claw of a lobster,fo
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