I56 A NATURAL HISTORY OF THE SEAS 



as the fish attains maturity. A particularly interesting 

 feature of this fish is the very obvious cause of its retrograde 

 development. Several other species of closely similar 

 Gobies frequent the same reef and similarly seek refuge 

 in the burrows of crustaceans. But whereas these forms 

 enjoy a wide range and only take shelter when danger 

 threatens, the blind species is highly localised and never 

 leaves its retreat. It is evidently therefore a degenerate 

 relative which has paid for its want of enterprise in the 

 loss of eyesight and generally poor development. 



Few subjects have been more obscured by poetic fancy 

 — -as opposed to scientific fact — than have the migrations 

 of various animals. As regards fishes, accurate data is 

 still lacking as to the precise movements of many quite 

 common species, though in this direction up-to-date 

 research with all the wonderful appliances now at its 

 command is making remarkable progress. 



The latest work in this direction has been undertaken 

 by the French Government, who recently sent a fisheries 

 research mission into the Atlantic under the directorship 

 of Monsieur Jean le Danois. The expedition asserts that 

 there is evidence that Great Britain once joined the 

 European continent, and that the Rhine once had its 

 outflow near the Firth of Forth, an assertion which casts 

 an interesting light on the movements of two fish, namely 

 the Haddock (Gadus aeglefinus) and the Tunny (Thynnus 

 thynnys), which have long been known to make periodic 

 journeys from the Atlantic into Continental waters. 

 These fish, one would imagine, would, in order to enter the 

 North Sea from the Atlantic, take the short cut offered 

 by the English Channel. They, however, still travel 



