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III. — Polychaeta of the family Nereidse, collected by the Scottish National 

 Antarctic Expedition (1902-1904). By L. N. G. Ramsay, M.A., B.Sc, Carnegie 

 Research Scholar, Christ's College, Cambridge. Communicated by Dr. J. H. 



ASHWORTH. 



(MS. received October 7, 1913. Read December 15, 1913. Issued separately March 30, 1914.) 



[Plate III.] 



The collection of Nereidse brought home by the Scotia proves to be of considerable 

 interest. As other expeditions have indicated, the family is but poorly represented in 

 the antarctic or sub-antarctic regions ; and although a large number of specimens were 

 collected at the South Orkney Islands, these have all proved to belong to one species, 

 N. kerguelensis M'Int. No nereids were obtained at any of the deep-water stations 

 farther south — the family being decidedly littoral in its range. 



The chief interest, however, lies in the material collected so assiduously throughout 

 the vessel's wanderings. Six other species were obtained, including one from the 

 Falkland Islands, hitherto und escribed. 



The investigations of the more recent workers on the Nereides continually tend to 

 widen the distribution of hitherto known species, and to link up forms which have been 

 described as distinct — in some cases apparently from the supposition that it was incon- 

 ceivable that one and the same species could inhabit areas so widely separated as, say, 

 the Indian Ocean and the North Atlantic. It is becoming more and more evident, 

 however, that in the determination of species, locality must not be taken into account. 

 Several species are already recognised as having a range that is practically cosmopolitan 

 (e.g. N. dumerilii, from the North Atlantic, North Pacific, and Persian Gulf; N. mirabilis, 

 from the West Indies, Red Sea, Persian Gulf, and Malay Archipelago). It is therefore 

 clear that the world-wide distribution of any particular species is a contingency that 

 must be reckoned with. 



The means of dispersal which render this world-wide distribution possible can only, 

 for the present, be a matter of surmise ; the carriage of pelagic larvse by ocean currents 

 may be sufficient to account for it ; and in this connection, also, the investigations of the 

 Scotia naturalists supply a very suggestive hint in the discovery of nereids living and 

 breeding among floating gulf-weed in mid-Atlantic. These, it may be noted, have been 

 described as a variety of the species N. dumerilii. 



The excellent condition of the Scotia material has rendered its examination and the 



determination of the species comparatively easy. The descriptions following are in no 



case based on a single specimen ; where only a few specimens were found, these were all 



examined in detail ; where examples were numerous, the individual variation has been 



taken into account. This is of considerable importance, as the great latitude of indi- 

 TRANS. ROY. SOC. EDIN., VOL. L. PART I. (NO. 3). 6 



