224 FOOT-NOTES TO EVOLUTION. 



in common that the coral reefs, rocky islands, and tide 

 pools of the tropics have not ? 



Fig. i6. — Skeleton of the spotted greenling {Hexagrammos decagram- 

 mus). From nature, by W. S. Atkinson. A northern fish, with 

 vertebrae numerous and small. 



In this connection we are to remember that the fewer 



vertebrae indicates generally the higher rank. When 



vertebrae are few in number, as a rule 



Fewer vertebras - • i t 



. ,. each one is larger. Its structure is more 



indicates greater ,. ^ . 



specialization. complicated, Its appendages are larger 



and more useful, and the fins with which 

 it is connected are better developed. In other words, 

 the tropical fish is more intensely and compactly a fish. 



Fig. 17. — Skeleton of the scarlet rock-fish {Sebastodes miniatus). From 

 nature, by W. S. Atkinson. A species of temperate waters ; the 

 vertebrae in moderate number. 



with a better fish equipment, and in all ways better fitted 

 for the business of a fish, especially for that of a fish that 

 stays at home. 



