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Observations on the structure and propagation of the genus Sagitta.— By Charles Darwin, F.R.S., V.P.G.S.

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The species of this genus are remarkable from the simplicity of their structure, the obscurity of their affinities, & from abounding in infinite numbers over the intra-tropical and temperate seas. The genus was founded by MM. Quoy and Gaimard* (a); three species have been figured & described by M. A. d'Orbigny, & lately Prof. E. Forbes has added a species to the British fauna, & has given many particulars reg the structure of the genus. Scarcely any pelagic animal is more abundant - I found it in Lat. 21° N. in the Atlantic, & again off the coast of Brazil in 18° S; between latitudes 37° and 40° S., the sea, especially during the night swarmed with them. They generally appear to swim near the surface; but in the Pacific off the coast of Chile, I obtained specimens from a depth of four feet. They are not confined exclusively to the open ocean, as supposed by M. d'Orbigny; for near the shore of Patagonia, where the water was only ten fathoms in depth, they were very numerous.

All the individuals which I caught had two pairs of lateral fins; but I do not

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(note)

* Annales des Science Naturelles Tom X p. 232 M. A' Orbigny's observation are given in his grand work (Mollusque p 140) Prof. E. Forbes from years since made his first communication this genus before the Wernerian Society & a second one at the meeting of the British Association for the present year.

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Proofs lettering under [illeg]

I calculated 2500 words = 3s n 3d

2640 [-] 132 [=] 2508

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