12 



HJALMAR BROCH. 



[REP. OF THE "MICHAEL SARS" NORTH 



With few exceptions the species have been found in 

 the Mediterranean too. These exceptions are Perigonimas 

 Jonesi, Nemertesia Hartlaubi, Sertularella cylindritheca 

 and Campanularia mutabilis, not taking into consideration 

 the doubtful specimens of Nemertesia rugosa and Lao- 

 medea bijurca. Sertularella cylindritheca seems to be a 

 rather rare species in the eastern Atlantic, being hitherto 

 recorded only from two localities by the "Travailleur" and 

 "Talisman". Perigonimus Jonesi was previously recorded 

 only from the western side of the Atlantic. Nemertesia 

 Hartlaubi had only been obtained from the Suldanha 

 Bay (Cape Colony), and Campanularia (?) mutabilis from 

 the Cape Verde Islands. 



The "Michael Sars" material confirms the opinion 

 expressed in previous papers 1 ) that the fauna of the 

 Mediterranean has immigrated from the Atlantic, the 

 concordance between the Atlantic and the Mediterranean 

 faunas being far greater than that between the Mediter- 

 ranean and the Indian Ocean faunas. 



Our material shows furthermore that the faunistic- 

 differences between the eastern and western sides of the 

 Atlantic may prove to be less important than hitherto 

 supposed, but it is greatly to be desired that renewed 

 investigations should be undertaken on the American 

 side too. 



The Hydroids of The Drifting Sea-weed 



taken during the cruise of the "Michael Sars" belong to 

 the following six species: 



Plumularia caiharina. 

 Aglaophenia lale-carinata. 

 Sertuldria distans. 

 Campanularia Johnstoni. 



simplex. 

 Laomedea sargassi. 



Plumularia catharina and Campanularia Johnstoni 

 afford little assistance in answering the question as to the 

 origin of the Sargasso fauna, because they are widely 

 distributed as bottom-animals. 



Of the remaining four species we know that Sertularia 

 distans and Laomedea sargassi live as bottom-animals 

 in the West-Indies and round the Azores, whereas Aglao- 

 phenia late-carinata and Campanularia simplex are pre- 

 dominant inhabitants of the floating sea-weed round the 

 West-Indies, and have also been recorded from the Mexican 

 Gulf. These data give us an idea as to the geographical 

 origin of the Sargasso hydroid fauna. The hydroids of 



the Sargasso sea have been carried with the drifting sea- 

 weed from the tropical parts of the Atlantic, especially 

 from the West-Indies, possibly also to some extent from 

 the Azores. The colonies are carried away from these 

 places as fixed stages; larval transport does not seem to 

 play any important part in this connection. 



The characteristic hydroids of the drifting Sargasso 

 weed are, after all, confined within narrow limits, fixed 

 by small hydrographical differences; the Sargasso hydroids 

 generally do not enter the Norwegian Sea except such 

 rather cosmopolitan forms as Campanularia Johnstoni and 

 Plumularia catharina, which must be regarded as typical 

 southern guests in Norwegian waters. It will in this con- 

 nection be of interest to give some of the results of previ- 

 ous investigations, especially of the "Michael Sars", as to 



The Occurrence And Distribution Of Southern Hydioids 

 In The Norwegian Sea And The North Sea. 



The general faunistic features of Norwegian waters, 

 and especially those of the arctic regions, have been the 

 subject of several treatises of later days. Recently Appel- 

 lof 2 ) gave a review of the principal results as regards 

 the bottom-animals of the Norwegian Sea and the North 

 Sea, but the special forms of the warmer waters of the 

 Atlantic (the "lusitanic" forms) were only incidentally 

 mentioned, whereas the arctic and subarctic ("boreal") 

 animals were discussed thoroughly. The lusitanic factor 

 plays a great and interesting part in the general features 

 of Norwegian waters, and Gran 3 ) paid great attention to 

 it in his fundamental work on the plankton of the Nor- 

 wegian Sea. 



If we attempt to trace the occurrence of lusitanic 

 bottom species in the Norwegian Sea, we soon discover 

 that our knowledge is very deficient in regard to the 

 continental edges along the Norwegian coast, especially 

 to the north of Stat. The accompanying map (fig. 14) 

 showing the distribution of many southern hydroids veri- 

 fies this fact, for it includes all the species of PI urn u- 

 lariidae and Aglaopheniidae, which must be 

 regarded as warm water forms, recorded from Norwegian 

 waters. We should not expect the rather sporadic occur- 

 rence of these numerous species, which have been the 

 object of special study, particularly by the two investiga- 

 tors M. and G. O. Sars. The map contains sufficient 

 data to give a good idea of the general features of the 

 distribution of atlantic hydroids in Norwegian waters. 

 Like southern planktonic animals the southern bottom 

 animals are mainly confined to the Atlantic, and limited 



') KOKENTHAL und Broch, Pennatulacea (Wiss. Ergebn. d. deutschen Tifsee-Exped. "Valdivia", Bd. XIII) Jena 1911, p. 469. Broch, 

 Hydroiduntersuchungen III, p. 63. 



2 ) Havbundens dyrcliv (Norges fiskcrier. I. Norsk havfiske). Bergen 1905. 



•') Das Plankton des norwegischen Nordmeeres (Report. Norw. Fish- and Mar. Invest. Vol. II). Bergen 1902. 



