Temperature and Vertebra 21 



In general, we maj' sky of the soft-rayed fishes that very 

 few of them are inhabitants of tropical shores. Of these few, 

 some, which are closely related to northern forms, have 

 fewer vertebra than their cold-water analogues. In the 

 northern species, the fresh-water species and the species found 

 in the deep sea, the number of vertebrae is always large, but 

 the same is true of some of the tropical species also. 



Spi7iy-rayed Fishes. — Among the spiny-rayed fishes, the 

 facts are more striking. Of these, numerous familes are 

 chiefly or wholly confined to the tropics, and in the great 

 majority of all the species the number of vertebrae is con- 

 stantly 24,* 10 in the body and 14 in the tail (10+14). 



In some families in which the process of ichthyization has 

 gone on to an extreme degree, as in certain plectognath 

 fishes, t there has been a still further reduction, the lowest 

 number, 14, existing in the short inflexible body of the 

 trunkfish,! i'l which the vertebral joints are movable only in 

 the base of the tail. In all these forms, the process of reduc- 

 tion of vertebrae has been accompanied by specialization in 



* This is true of all or nearly all the SerranidcE, Sparidez, Scicsnidcs, 

 Chcstodontidcs, HceinulidcE, Gerridcs, Gobiidcs, Acanthuridcs, Mugi- 

 lidiz, Sphyrixnidcs, Mullidce, Pontacentridcs , etc. 



t Batistes, the trigger fish, 17 ; Monacanthus and Alutera, foolfishes, 

 about 20; the trunkfish, Ostracion, 14; the puffers, Tetraodon and 

 Splieroides, 18; Catiitiigaster, ij \ and the headfish, TJ/o/a, 17. Among 

 the Pedicutates, Malt/ie and Aiiteniiarius have 17 to 19 vertebne, while 

 in their near relatives, the anglers, Lophiidis, the number varies with the 

 latitude. Tims, in the northern angler, Loptiius piscatorius, which is 

 never found south of Cape Hatteras, there are 30 vertebrse, while in asimi- 

 larspecies, inhabiting both shores of the tropical Pacific, Lop/iiomus seti- 

 geriis, the vertebrae are but 19, Yet, in external appearance, these two 

 fishes are almost identical. It is, however, a notable fact that some of 

 the deep-water Pedicutaies, or angling fishes, have the body very short 

 and the number of vertebrse correspondingly reduced. Dibranchus 

 attanticus, from a depth of 3,600 fathoms, or more than 4 miles, has 

 but iS vertebrae, and others of its relatives in deep waters show also 

 small numbers. These soft-bodied fishes are simply animated mouths, 

 with a feeble osseous structure, and they are perhaps recent offshoots 

 from some stock which has extended its range from muddy bottom or 

 from floating seaweed to the depths of the sea. 



.| Ostracion. 



