PELAGIC ANIMAL LIFE 



569 



is short and they die unless they reach the bottom within a certain 

 Hmited time. 



Damas and Koefoed ^ mention as the most important forms in 

 Scandinavian waters the following species : Sarsia tubulosa, S. eximia, 

 Euphysa aurata, Cojymorpha nutans, Hybocodon prolifer, Bougainvillia 

 superciliaris var., Dysmorphosa octopunctata, Tiara pileata, Limneandra 

 norvegica, Melicertidiinn octocostatiim, different species of Obelia and 



Fig. 396. 



Hydroid colony of Syncoryne pulchella. 



(From Allman. ) 



Fig. 397. 



Medusa, just after leaving 



colony. 



Phialidiiim, Mitrocoinella fiilva, Tiaropsis viulticirrata, and Lutonia 

 socialis. From the Arctic plateau between Spitsbergen and Bear 

 Island they mention Sarsia flammea, Codoniuvi princeps, Catablema 

 campanula, Hippocrene superciliaris (see Fig. 398). These forms do not 

 play any part in the fauna of the open ocean. 



The Trachymedusae have a direct development without a hydroid or 

 bottom stage. In northern waters we meet with only one species in such 

 numbers, and so frequently, that it may be considered truly northern 



^ Damas et Koefoed, " Le Plancton de la Mer de Greenland," Due d'Orleans' Croisiere 

 occanogyaphique (Bruxelles, 1905). 



