V ril Bestemmelsen af Aimelider fra det af den norske 

 Nordhavsexpedition afsøgte Felt er det selvfølgeligt 

 hovedsageligt Malmgrens "Annulata polychæta", der maa 

 benyttes. San værdifuldt som dette Arbeide er. saa van- 

 skeligt og oftest umuligt er det at bringe et ukjendt Dyr, 

 som man maatte træffe paa, ind under en af de mange af 

 Malmgren opforte Slægter. Om denne Malmgrens Tilbøie- 

 ligbed til at danne nye Slægter efter ofte meget uvæsent- 

 lige Karakterer have allerede flere Forfattere udtalt sig 

 og senest Dr. , Théel 1 , der nævner Polynoidæ, Syllidæ 

 Nereidæ, Ampharetidæ og Terebellidæ som Familier, hvor 

 der fornemmeligst tiltrænges en betydelig Reduktion eller 

 ialfald Modification af de malmgrenske Slægter. 



Jeg har om de fleste af disse Familier ikke saa tal- 

 rige selvstendige Undersøgelser og Erfaringer at stotte 

 mig til. at jeg kan udtale mig ganske bestemt herom; men 

 for Polynoidemes Vedkommende tor jeg med Sikkerbed. 

 sige. at naar Malmgren har delt disse Dyr, der have en 

 saa paafaldende Lighed med hinandeii indbyrdes, i ikke 

 mindre end 18 Slægter. af hvilke flere kun ere repræsen- 

 terede ved en enkelt Art. da er en saa vidtgaaende Son- 

 dring ikke alene unødig, men ogsaa hoist uberettiget. For 

 at overbevise sig herom behøver man blot at gjøre, som 

 Mobius har gjort, idet han søger at vise at Harmothoe 

 imbricata, Evarne impar, Lamilla glabra, Ant/noe Sarsi 

 kun ere forskjellige Navne paa samme Dyr, nemlig stille 

 ved Siden af binanden Malmgrens Diagnoser af de for- 

 skjellige Slægter og bestræbe sig for at linde ud af. hvori 

 Forskjellen mellem dem egentlig bestaar. Man vil strax 

 komme i Forlegenhed hermed og man bliver ikke bedre 

 stillet, om man specielt soger efter de Kjendetegn. som 

 Malmgren selv siger at have benyttet foråt karaktisere 

 Slægterne, nemlig Skællenes Antal og den Maade, paa 

 hvilken di' bedække Ryggen. Hovedlappens Fonn og An- 

 tennernes Befæstningsmaade, og endelig Børsterne; disse 

 sidste synes Malmgren især at hegge Vægt paa. thi han 

 siger: "De Genuskarakterer. som kunna hentas tran fot- 



'.Hj. Théel. Les annélides polychétes des mers de la Nouvelle- 

 Zemble. Stockholm 1879. 



Den norske Nordhavsexpedition. (i A Hansen: Annelida. 



In working out the Annelids collected on the Nor- 

 wegian North-Atlantic Expedition, Malmgrens "Annu- 

 lata polychæta" would of course be the chief book of reference. 

 But. whatever the intrinsic value of this well-known work, 

 it is difficult, nay. in the great majority of cases impos- 

 sible, to class an unknown Annelid under one of the 

 many genera instituted by Malmgren. The tendency in 

 that distinguished zoologist to establish new genera from 

 non-essential characters, has been previously noticed by 

 several authors, the latest being Dr. Théel. ' who enumer- 

 ates the families Polynoidæ, Syllidæ, Nereidæ, Ampharetidæ, 

 and Terebellidæ as those in which the Malmgren genera 

 are more particularly in need of being reduced in number, 

 or at least diagnostically modified. 



My autoptical acquaintance with most of these fami- 

 lies is indeed too limited to admit of pronouncing decisively ; 

 but as regards the Polynoidæ. I do not hesitate to affirm 

 that, in dividing these animals, which bear so striking a 

 resemblance to one another, into no less than 18 genera. 

 many of them represented by only a single species. Malm- 

 gren has laid himself open to the charge of introducing 

 needless and suppositious distinctions. And proof of this 

 is readily furnished by instituting a comparison. — ■ as did 

 Mobius. when seeking to show that Harmothoe imbricata, 

 Evarne impar, Lænilla glabra, Ant/noe Sarsi are merely 

 different names for the same animal. — between Malmgrens 

 diagnoses of the numerous genera, with a view to discover 

 wherein their alleged difference actually consists. But this 

 is no easy matter: the perplexing nature of the attempt 

 becomes at once apparent. Nor does it anyway avail to look 

 for the various criteria selected by Malmgren for characte- 

 rising the genera, viz. the number of the scales and their 

 arrangement on the back, the form of the lobes of the 

 head, the mode of attachment of the feelers, and finally, 

 the bristles. To the latter Malmgren attaches, it would 

 seem, special weight, as will appear from the following 

 remarks: -'The distinctive features furnished by the 



structure of the pedal bristles are in my opinion the most 



' Hi. Théel. Les annélides polychétes des mers de la Xonvelle- 

 Zemhle. .Stockholm 1879. 



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