First lesson in zoology : adapted for use in schools . imming feet of thehind body. The young (Fig. 88) are hatched with much ofthe form of the adult, not passing through a series of sin-gular changes, called a metamorphosis, as do most shrimpsand crabs. They swim near the surface until about oneinch long, afterwards remaining at or near the bottom. The lobster, after having nearly grown up, probablymoults but once, during midsummer. When about to 86 FIRST LESSONS IN ZOOLO&Y. moult, or cast its skin, the shield splits from its hind edgeas far as the base of the beak, where it is too solid to s
First lesson in zoology : adapted for use in schools . imming feet of thehind body. The young (Fig. 88) are hatched with much ofthe form of the adult, not passing through a series of sin-gular changes, called a metamorphosis, as do most shrimpsand crabs. They swim near the surface until about oneinch long, afterwards remaining at or near the bottom. The lobster, after having nearly grown up, probablymoults but once, during midsummer. When about to 86 FIRST LESSONS IN ZOOLO&Y. moult, or cast its skin, the shield splits from its hind edgeas far as the base of the beak, where it is too solid to sepa-rate. The lobster then draws its body out of the claw—at this time soft, fleshy, and very watery—isdrawn out through the first joint, part of which disappearsat this time, so as to make room for the passage of theflesh of the big claw. In moulting, the stomach, with thesolid teeth, is cast off with the old crust or skin. Haying looked with some care at the lobster, we canglance more hastily at some of its allies. Its nearer rela-. Fia. 90.—Young, or Zoga, of Cancer irrora- Fig. 91.—Megalops, or older stage,tus. (Highly magnified.) of Fig. 90. (Magnified.; tions are the crabs, and of these there are many kinds. Incrabs the hind body is very small and folded to the underside of the chest. The common shore-crab (Fig. 89) livesunder stones, where it may be found at low-water the tide comes in it may be seen running sidewaysin a comical fashion over the bottom. If we compare the crab with the lobster we see a greatadvance; the crabs head and mid-body are much better de-veloped, while its hind body is small and folded to the un-der side of the chest. There is a transfer of parts head-wards, a great step onwards and upwards. THE LOBSTER AND OTHER CRUSTACEANS. 87 A curious creature is the hermit-crab (Fig. 92). Select-ing an empty shell, it thrusts its soft hind body into it, and
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1894
