116 BRAIN AND BODY OF FISH 



THE ACOUSTIC TUBERCLES IN DEEP-WATER FISHES 



In the previous pages the unusual pattern of the cerebellum and 

 acoustic tubercles of the hake has been figured and described, and a 

 tentative suggestion was made that the large development of the 

 acoustic tubercles might be due to the great depths (300 to 400 

 fathoms) in which this fish has been found. An opportunity haa 

 since arisen of investigating the pattern of the brain of fishes which 

 descend to great depths, even a mile down, and we propose to des- 

 cribe the remarkable confirmation of the theory that was advanced 

 to explain the brain -pattern of the hake. 



The warm waters of the Atlantic provide the Madeira fishermen 

 with a rich harvest in the spring of " Espada," the black scabbard- 

 fish (Aphanopus carbo), which is often so plentiful, that a fish 

 several feet long can be bought for sixpence. Incidentally, it may 

 be recorded that my ignorance was so great that I paid a sliilling 

 for a head, to the great joy of both merchant and my friends. This 

 fish is caught at depths of 600 to 1,600 metres, and always is brought 

 to the surface dead. 



Lying on the slabs of the fish-market these fish appear sheathed 

 in a skin of black patent leather, shiny and without scales, elongated 

 like an eel, with the body compressed rather than round ; the dorsal 

 fin extends as a continuous fringe from head to tail, the eyes are 

 very large, as big in circumference as a half-a-crown, while a fear- 

 some looking head gives support to large and long jaws, both upper 

 and lower of which bear large and prominent teeth. A bite from 

 these fish is accompanied with very severe bleeding, and the blood 

 from the gills is said to produce inflammation, so that the after- 

 results are marked on the fisherman's disfigured hands. 



The caudal fin is very small, and there is a narrow constriction 

 separating this diminutive forked tail from the body. The penalty 

 for its large eyes and small tail, is for its dead body to be carried 

 home with the tail tlu-eaded through the empty sockets, according 

 to the cook's technique with the whiting. Both fish are very good 

 eating. 



This fish, and the others I shall shortly mention, belong to the 

 cutlass-fishes or hair-tails (Family : Trichiurida?), and curiously 

 enough are distantly related to the mackerel and tunny, the forked 

 tail being the only superficial resemblance that is left. But it is 

 interesting to note that on the same day, in the same market, are 

 to be seen large numbers of tunny and mackerel, and also horse- 

 mackerel and other carangida^, together with rows and rows of 

 Espada. 



