10 FISHES OF THE VICINITY OF NEW YORK 



side of the mid-line, in the order given. The sense organs communi- 

 cate by nerves with the "central" or brain, where the signals received 

 from the sense organs are sorted out; and from whence new or induced 

 nerve currents are sent out to the machinery of the body. Sense 

 organs, brain and connecting nerves are all inclosed in strong bony 

 capsules and troughs which make up the inner skull, or endocranium. 

 The roof of this structure is formed by the bony skull plates above 

 described, and it is strongly braced below by a sort of keel called the 

 parasphenoid bone (Fig. 3). At the rear the inner skull is securely 

 joined to the backbone. The skull must of necessity be strongly built 

 in order to resist the thrust of the backbone, as the body is driven 



Fig. 4. CROSS SECTION OF SKULL OF DRUM-FISH 

 Showing inner skull (cross-hatched) and roof of brain-case (white). 



forward through the water. In primitive fishes the inner skull and the 

 outer skull are fairly distinct and the outer plates may be stripped 

 off after boiling or macerating the skull; but in the higher fishes, such as 

 the bass, the outer skull plates sink beneath the skin and become welded 

 with the inner skull (Fig 4). 



From this stiff and immovable part of the head is suspended 

 a complex apparatus, by means of which- the food is seized and water i= 

 taken into the throat to pass over the gills and out through the gill 



