INTRODUCTION 



with remarks on the classification etc. 



The following paper deals with the liydroids obtained by the Danmark 

 Expedition to North-East Greenland in 1906—1908. Whilst the 

 ship was stationed at Danmarks Havn, 76° 46' N. L., 18° 14' W. L., 

 the zoologist of the Expedition, Mr. Fritz Johansen, made several 

 excursions into the surrounding fjords and sounds and collected 

 among other things a large material of hydroids. When the Expe- 

 dition left for the home-voyage in the summer of 1908, a number 

 of stations in deep water were investigated; at only three of these 

 were hydroids found, namely, at the trawl stations 96, 99 and 104 b. 



I have now worked through this large material; it contains 33 

 species, 3 of which are new. 



I have not ventured to discuss the zoogeographical interest of 

 the material, though it is certainly considerable, as there is still a 

 large material of hydroids from the east coast of Greenland, which 

 is not yet worked up. 1 have restricted myself to drawing up table 

 7, which displays the principal points in this connection of the zoo- 

 geographical conditions of the species mentioned. In the text I give 

 a brief review of the geographical distribution of each species, refer- 

 ring at the same time to the papers of Jäderholm and Broch of 

 1909, (35) and (17). Jäderholm publishes precise information re- 

 garding the places where the species were found; Broch has drawn 

 up some very practical lists showing the zoogeographical conditions 

 for the arctic species. 



With regard to the classification, I follow in the main the 

 lead given by Levinsen, 1892 (38), which for the northern species 

 has been carried further especially by Broch. In classifying we 

 should naturally always pay attention to as many characters as pos- 

 sible; but in seeking to clear up the classification of the hydroids 

 we often come into a difficult position, especially when the tropho- 

 somes are in very close agreement in species which show different 



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