GENERAL FACTS ABOUT SEA FISH 15 



at all. They contain much lime, and may more aptly be 

 compared with teeth. In fact, in the embryo of some sharks, 

 before the development of the lip, these granulations of the 

 skin are actually continued into the mouth and there form 

 the beginnings of teeth. 



The lateral line may be regarded as a system of modified 

 scales, perforate and communicating with cells of a gelatinous 

 The Lateral Substance so, in all probability, as to constitute 

 Line. ^ most Complex and important sense-organ with 

 functions that have not yet been more than vaguely deter- 

 mined. Formerly the duty of the lateral line was thought to 

 begin and end with the lubrication of the body with mucous, 

 but this very simple view of its purpose has long been super- 

 seded. Day and, later, Cunningham and others agree that the 

 lateral line is usually wanting in fishes of the herring family ; 

 but the late Matthias Dunn, two years before his death, drew 

 the writer's attention to its unquestionable presence in the 

 pilchard. While on this subject, it would be unreasonable to 

 overlook a most interesting article contributed by that remark- 

 able observer to the Contemporary Review (August, 1899), 

 entitled " The Seven Senses of Fishes." It may be that, in 

 his zeal to advocate his two extra senses in fishes, Dunn went 

 somewhat boldly, even a little wantonly, out of the well- 

 trodden rut of modern research. It may even be that later 

 investigations may not tend to confirm his theories. Yet 

 even such a result would take nothing from the interest of 

 his watchfulness and reasoning powers. The sixth and seventh 

 senses which he claimed for fishes were termed respectively the 

 electric and magnetic " dermal " sense, and he describes the 

 first as one of weather forecast, and a second as a kind of bump 

 of locality under water, the sense being in both cases resident 

 in the lateral line. He regarded the brain of a fish, in fact, as 

 a counterpart of Lord Kelvin's compass-magnet floating in a 

 liquid, and he thought it might be sensibly affected by the 

 long-recognised magnetic properties of the grim Cornish head- 



