i6 SALT-WATER FISHES 



lands, which have so often caused fatal deflections of ships' 

 compasses. 



To the sternly academic mind the inferences in the article 

 under notice may seem a trifle far-fetched ; but it was quite 

 impossible for a man of Dunn's restless intelligence to con- 

 template the regular wanderings of the pilchard shoals for fifty 

 years without making some attempt at finding a solution of 

 the mystery of their return, year after year, along exactly the 

 same course. It was equally impossible that he would be 

 deterred from such attempt by any self-consciousness or by 

 fear of ridicule. 



The lateral line is more or less conspicuous, as a rule, 

 through a great portion of its length, being, even in closely 

 related fishes, either black (as in the haddock) or white (as in 

 the cod), while in the scad it is flanked by rows of very rough 

 scales. It does not end at the point where the eye sees it 

 no longer, just behind the neck; but, disappearing below the 

 surface of the skin, it branches over the head, and probably 

 conveys to the brain the sensations communicated along its 

 pores. Much, however, of what is written in connection with 

 this characteristic organ of fishes is in the nature of pure 

 speculation, and a full and exhaustive study of its properties 

 has yet to be made. When made, it will be interesting in 

 the extreme. 



We must now briefly examine a number of external 

 characters of fishes in the region of the head — the eyes, 

 _ nostrils, ears, mouth and teeth, gills and gill-covers. 



Teeth,Gills, As Seen in the bass (^Labrax) or cod {Gadus), 

 the typical head of a fish is, roughly speaking, in the 

 form of a wedge, with the line between the gill-covers for 

 base and the lips for apex. The departures, however, from 

 this simple form are so many and varied that considerations 

 of space must restrict the list of exceptions to such few as the 

 conical head of the skates (Raia), the beaked head of the gar- 

 fish CBekne), the twisted head of the plaice {Tleuronectes), the 



