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By an increase in the size of this projection, with its shape, as well as that of the terminal segment, slightly modified and improved, the pincers are rendered more and more perfect, until we have at last an instrument as efficient as the chelae of a lobster. And all these gradations can be actually traced. Besides the avicularia, the polyzoa possess curious organs called vibracula.
As the chelae of Crustaceans resemble in some degree the avicularia of Polyzoa, both serving as pincers, it may be worth while to show that with the former a long series of serviceable gradations still exists.
A curious resemblance, though less in degree, has also been seen to exist between the auditory organs of fishes and of Cephalopods. Remarkable similarities between certain placental and implacental mammals, between the bird's-head processes of Polyzoa and the pedicellariæ of Echinoderms, between Ichthyosauria and Cetacea, with very many other similar coincidences, have also been pointed out.
Such are the corals; those corallines which are called Polyzoa; those creatures which fabricate the lamp-shells, and are called Brachiopoda; the pearly Nautilus, and all animals allied to it; and all the forms of sea-urchins and star-fishes.
The beak opens and shuts at intervals, like the jaws of the pedicellariæ of the echinus, and there is altogether, in general principle, a remarkable similarity between the structures. Yet the echinus can have, at the best, none but the most distant genetic relationship with the Polyzoa. We have here again therefore complex and similar organs of diverse and independent origin.
Réaumur, admitting the analogy indicated by Peyssonel, gave the name of polypes, not only to the sea-anemone, the coral animal, and the fresh-water Hydra, but to what are now known as the Polyzoa, and he termed the skeleton which they fabricate a "polypier" or "polypidom."
Mivart adduces this case, chiefly on account of the supposed difficulty of organs, namely the avicularia of the Polyzoa and the pedicellariae of the Echinodermata, which he considers as "essentially similar," having been developed through natural selection in widely distinct divisions of the animal kingdom.
Reaumur, admitting the analogy indicated by Peyssonel, gave the name of polypes, not only to the sea-anemone, the coral animal, and the fresh-water Hydra, but to what are now known as the Polyzoa, and he termed the skeleton which they fabricate a "polypier," or "polypidom."
But A soon broke up into two principal stirpes, of which one, a, became the root of the Annelida, Echinodermata, and Arthropoda, while the other, b, gave rise to the Polyzoa and Ascidioida, and produced the two remaining stirpes of the Vertebrata and the Mollusca.
Polyplectron, number of spurs in; display of plumage by the male; gradation of characters in; female of. Polyplectron chinquis. Polyplectron Hardwickii. Polyplectron malaccense. Polyplectron Napoleonis. Polyzoa. Pomotis. Pontoporeia affinis. Porcupine, mute, except in the rutting season. Pores, excretory, numerical relation of, to the hairs in sheep. Porpitae, bright colours of some.
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