Adaptations of Fishes 209 



looormore; Lumpenus, 79; Pholis, 85; Lycodes, 112; Gymnelis, 

 93. Lycodes and Gymnelis have lost all the dorsal spines. 



In the cod family (Gadidce) the number of vertebrae is usu- 

 ally about 50. The number is 51 in the codfish (Gadus callarias), 

 58 in the Siberian cod (Eleginus navaga), 54 in the haddock 

 (Melanogrammus czglifinus), 54 in the whiting (Merlangus mer- 

 langus), 54 in the coalfish (Pollachius virens), 52 in the Alaskan 

 coalfish (Theragra chalcogramma) , 51 in the hake (Merluccius 

 merluccius}. In the burbot (Lota lota), the only fresh-water 

 codfish, 59; in the deep-water ling (Molva molva}, 64; in the 

 rocklings (Gaidropsarus} , 47 to 49. Those few species found 

 in the Mediterranean and the Gulf of Mexico have fewer fin-rays 

 and probably fewer vertebrae than the others, but none of the 

 family enter warm water, the southern species living at greater 

 depths. 



In the deep-sea allies of the codfishes, the grenadiers or 

 rat-tails (Macrourida}, the numbers range from 65 to 80. 



Fresh-water Fishes. Of the families confined strictly to 

 the fresh waters the great majority are among the soft-rayed or 

 physostomous fishes, the allies of the salmon, pike, carp, and 

 catfish. In all of these the vertebrae are numerous. A few 

 fresh-water families have their affinities entirely with the more 

 specialized forms of the tropical seas. Of these the Centrarchida 

 (comprising the American fresh-water sunfish and black bass) 

 have on the average about 30 vertebrae, the pirate perch 29, 

 and the Percidaz, perch and darters, etc., 35 to 45, while the 

 Serranidcs or sea-bass, the nearest marine relatives of all these, 

 have constantly 24. The marine family of damsel-fishes (Poma- 

 centridce} have 26 vertebras, while 30 to 40 vertebras usually 

 exist in their fresh -water analogues (or possibly descendants), 

 the Cichlidoz, of the rivers of South America and Africa. The 

 sticklebacks (G aster osteidce} , a family of spiny fishes, confined 

 to the rivers and seas of the north, have from 31 to 41 vertebrae. 



Pelagic Fishes. Among the free-swimming or migratory 

 pelagic fishes, the number of vertebrae is usually greater than 

 among their relatives of local habits. This fact is most evident 

 among the scombriform fishes, the allies of the mackerel and 

 tunny. All of these belong properly to the warm seas, and the 

 reduction of the vertebrae in certain forms has no evident rela- 



