178 HISTORY OF THE EUROPEAN FAUNA. 



prey to the currents of the sea. They have practically 

 no swimming organs, and only move by lashing to and 

 fro the tender cilia with which they are provided. 



This disposes, therefore, of Professor Credner's 

 main criticisms. As for the fauna of the relict 

 lakes, we are now only concerned with those of 

 Northern Russia, Finland, and Sweden. In the 

 lakes Wetter and Wener in the latter country 

 occurs the four-horned sting-fish (Coitus quadricornis y 



FlG. 14. The Four-horned Sting- fish (Coitus qitadricornis], reduced 

 from Professor Smitt's figure in the Fishes of Scandinavia. 



Fig. 14), which, as we have learned, also inhabits the 

 northern part of the Baltic, and, as was suggested, 

 migrated there at a time when the latter was 

 connected with the White Sea. The principal food 

 of this little fish consists in a marine Crustacean 

 called Idotea entomon, an animal allied to our 

 common woodlouse. This is a typical marine 

 species, but it occurs also in the relict lakes of 

 the countries mentioned above, as well as in the 

 Baltic and the Caspian. Perhaps the best known 



