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THE POPULAR SCIENCE MONTHLY.

specimens will give, to any one who can examine them, a better idea of the size, form, color, and general appearance of the birds; the metallic lustre, change of color, and delicate structure of their plumage, than any words or engravings can convey. They would furnish a definite outline that would much assist and guide the imagination in giving life to their forms, spirit to their actions, and reality to their finer traits of character, as developed in their native islands. But still all lifeless forms fail to come up to the living birds in a state of freedom. And we need not be surprised at the enthusiasm of the amateur, who observes them in all their freshness and beauty, sitting in the aromatic trees, feeding among the bushes, floating in the breeze on their gossamer-like plumes, or glancing through the groves like streaming meteors, in the exhilarating atmosphere of their own genial clime.

 

THE CHAIN OF SPECIES.
By Hon. LAWRENCE JOHNSON.

Part III.The Passage from Annulosa to Mollusca.

ANOTHER plan, however, is proposed, which seeks to connect Annulosa and Mollusca as successive stages in the progress of evolution from the simplest types and stages necessary to be taken in order to reach the highest development. This is the chain: Evolution of Protozoa directly into Annulosa; or first into the cœlenterate type and these into the annulose, either of which routes seems feasible and easy; then Annulosa into Mollusca; and then Mollusca into Vertebrata. Pursuing this road, the only difficulty of importance is the passage from the articulate or annulose form to the mollusk. Enough has already been said to furnish the key to all the other transitions, and the few brief minutes left us must be devoted to this really obscure problem. If the bridge erected here is practicable, it puts a different aspect upon the whole question, and reflects light backward and forward on every link of the chain.

As remarked, the only real difficulty is to connect annulosa and mollusca. For from cephalopods it is easy to develop the vertebrate type, by elongating the ventral aspect of the creature; and bringing down therewith the ventral portion of the cephalic appendages, which subsequently assume, or rather return to, the place and functions of lateral limbs to the main trunk; the other cephalic appendages, properly belonging to the neurohæmal axis, easily taking the form and offices of œsophagus, branchiæ, and even internal bronchial apparatus. Evolution of amphioxus in this way, from some lost octopus is easier to account for than from salpidæ, as proposed by recent authors; even