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in consequence of their former connection with the continent of 

 Asia possess a fish-fauna of which the most important elements, both 

 as regards quality and quantity, had no chance of further distribution 

 in an eastern direction. The rivers of the eastern islands of the 

 Archipelago were therefore almost devoid of fishes, and offered a 

 good place of abode for such forms as, though denizens of the sea 

 or of brackish water, possessed sufficient capacity for accommodating 

 themselves to a life in fresh-water. The competition of those Asiatic 

 forms (Cyprinidae, Mastacembelidae, Ophiocephalidae, Labyrinthici 

 etc.), originally better fitted for a fresh-water life, failing, everything 

 was in favour of the immigrants from the sea. The river-lishes of 

 Celebes favour this view, as also dues all that we know about the 

 fishes of Ternate, Ambon, Halmahera, etc. 



We observe the same phenomenon in the fresh waters of Australia. 

 These however contain also indigenous forms, partly very old, partly 

 younger forms; the latter were obviously, at least in part, marine 

 immigrants, which have accommodated themselves so entirely to a 

 fresh-water life as to adopt the characters of fresh-water fishes. 



The fauna of Australia enjoy at present a general and vivid 

 interest — are there not even people who believe that the cradle 

 of mankind stood there ? A remarkable point of interest in the 

 study of its fauna is the question how long Australia has been 

 isolated from other parts of the globe. New Guinea plays a pro- 

 minent role in answering this question. 



It is therefore a welcome fact that the Dutch New Guinea Expe- 

 dition of 1903 under the direction of Prof. A. Wichmann has brought 

 home, besides other treasures, a large collection of fishes from diffe- 

 rent lakes and many rivers and rivulets, giving us a good insight 

 into the fresh-water fauna of the northern part of the island. Ifwas 

 of great help to me, while studying this collection, that I was able 

 to make use of the fishes collected in the brackish water at the 

 mouth of the Merauke river, by Dr. Koch the medical man of the 

 Royal Geographical Society's Expedition to South New Guinea. The 

 results of this investigation will be published elsewhere, but some 

 more general conclusions may be mentioned here. 



When we reckon up all the fishes known up to the present date 

 from the lakes, rivers, and rivulets of New Guinea, we find that 

 their number amounts to more than 100 species, but only about 40 

 of these were found exclusively in fresh-water. 



A careful examination shews further that the latter species, with 

 a few exceptions, are either known from brackish or sea water at 

 other places, or that their nearest relatives may be found in brac- 



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