298 THE FISHES OF THE NORTHERN SEAS 



bore deeply into the tissues of their victims. The sea-lamprey (Petromyzon 

 marinus), like the rest of its kind, is a native of the North Atlantic, but the other 

 generic groups are restricted to the Southern Hemisphere. Hag-fishes have the 

 same distribution as the cod family, in the bodies of whose members they so fre- 

 quently take up their abode. The European Myxine glutinosa is confined to the 

 North Atlantic, where it is most common in the fiords of the Norwegian coast. 



The tiny, transparent fish-like creatures commonly known as 



Li.\IlC6l6tS. Till i* 



lancelets belong to a group standing on the borderland between 

 vertebrates and invertebrates. In the common \a,nce\et(Branchiostoma lanceolatum), 

 which is between 2 and 3 inches in length, the body is laterally compressed and 

 pointed at the two ends. There are no paired fins, but the back carries a long 

 dorsal, supported at the ends by gelatinous rays, and there is also a tail-fin ; the 

 lower part is similarly strengthened. Lancelets often bury themselves in sand, 

 but also swim in long chains composed of numerous individuals united together by 

 their heads and tails. 



THE LANCELET. 



