THE ANNALS 



AND 



MAGAZINE OF NATURAL HISTORY. 



" per litora spargite museum, 



Naiades, et circilm vitreos considite fontes : 

 Pollice virgineo teneros hlc carpite flores : 

 Floribus et pictum, divje, replete canistrum. 

 At vos, o Nymphse Craterides, ite sub undas ; 

 Ite, recurvato variata corallia trunco 

 Vellite muscosis e rupibus, et mihi conchas 

 Ferte, Dese pelagi, et pingui conchylia succo," 



Parthenii Eel. 1. 



No. 81. JANUARY 1844. 



I. — Observations on the Structure and Propagation of the genus 

 Sagitta. By Charles Darwin, F.R.S., V.P.G.S. 



[With a Plate.] 



The species of this genus are remarkable from the simplicity of 

 their structure, the obscurity of their affinities, and from abound- 

 ing in infinite numbers over the intra-tropical and temperate seas. 

 The genus was founded by MM. Quoy and Gaimard*; three 

 species have been figured and described by M. A. d^Orbigny, and 

 lately Prof. E. Forbes has added a species to the British fauna, 

 and has given many particulars regarding the structure of the 

 genus. Scarcely any pelagic animal is more abundant : I found 

 it in lat. 21° N. in the Atlantic, and again ofi" 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^Or- 

 bigny ; 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 pair of lateral fins, 



* Annales des Sciences Naturelles, torn. x. p. 232. M. d'Orbigny's ob- 

 servations are given in his grand work (Mollusques, p. 140). Prof. E. Forbes 

 four years since made his first communication on this genus before the Wer- 

 nerian Society, and a second one at the Meeting of the British Association 

 for the present year. 



Ann. ^ Mag. N. Hist. Vol. xiii. /B 



