568 THE POPULAR SCIENCE MONTHLY. 



specimens will give, to any one wlio can examine them, a better idea 

 of the size, form, color, and general appearance of the birds ; the me- 

 tallic 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. LAWEENCE JOHNSON. 

 Part III. — The Passage from Amiulosa to MoUusca. 



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 : Evolu- 

 tion of Protozoa directly into Annulosa; or first into the coelenter- 

 ate 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 tran- 

 sitions, 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 

 difierent 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, prop- 

 erly belonging to the neurohsemal axis, easily taking the form and 

 offices of oesophagus, branchia3, and even internal bronchial apparatus. 

 Evolution of amphioxus, in this way, from some lost octopus, is easier 

 to account for than from salpidoe, as proposed by recent authors ; even 



