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The occurrence of annelids is important, on account of their character and status in the animal kingdom. The Wenlock limestone is most remarkable amongst all the rocks of the Silurian system, for organic remains. Many slabs of it are wholly composed of corals, shells, and trilobites, held together by shale.
In this part of the body the skeletal ring of each segment is joined to that of the segments before and behind it in the same manner. But in other parts of the body we shall find the skeletal pieces of each segment and the rings of successive segments fused in one plate of mail. The legs are the parapodia of annelids carried to a vastly higher development.
These characters absent in the lowest classes Brilliant colours Mollusca Annelids Crustacea, secondary sexual characters strongly developed; dimorphism; colour; characters not acquired before maturity Spiders, sexual colours of; stridulation by the males Myriapoda.
Evidently then, corals, annelids, inferior molluscs, and crustaceans of low grade, will chiefly constitute the early Fauna.
Now I do not wish to conceal from you that many good zoölogists believe that the vertebrate is descended from annelids; but for this and other reasons such a descent appears to me very improbable.
Then the flat worms and mollusks took to a creeping mode of life, while the annelids and vertebrates still swam. Then the annelids settled to the bottom and crept, and all their descendants remained creeping forms. The vertebrates alone remained swimming, and probably neither they nor their descendants ever crept until they emerged on the land, or as amphibia were preparing for land life.
Quatrefages, A. de, on the occurrence of a rudimentary tail in man; on variability; on the moral sense as a distinction between man and animals; civilised men stronger than savages; on the fertility of Australian women with white men; on the Paulistas of Brazil; on the evolution of the breeds of cattle; on the Jews; on the liability of negroes to tropical fevers after residence in a cold climate; on the difference between field- and house-slaves; on the influence of climate on colour; colours of annelids; on the Ainos; on the women of San Giuliano.
But a complete development, such as already obtains in the lobster, &c., was reached by the Eurypterida and Trilobites of the palæozoic strata; and annelids, probably formed mainly like those of the present day, abounded during the deposition of the oldest fossiliferous rocks.
Three feet six nine, at least: with a capability of seemingly endless expansion; a slimy tape of living caoutchouc, some eighth of an inch in diameter, a dark chocolate- black, with paler longitudinal lines. Is it alive? It hangs, helpless and motionless, a mere velvet string across the hand. Ask the neighbouring Annelids and the fry of the rock fishes, or put it into a vase at home, and see.
The higher group includes the crabs, spiders, thousand-legs, and finally the insects, and forms the kingdom of arthropoda. The lower members are still usually reckoned as worms, and are included under the annelids. Of these our common earthworm is a good example, and near them belong the leeches. But the marine annelids, of which nereis, or a clam-worm, is a good example, are more typical.
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