VIII. 



LATITUDE AND VERTEBRA. 

 A STUDY IN THE EVOLUTION OF FISHES. 



IN this paper is given an account of a curious bio- 

 logical problem and of the progress which has been made 

 toward its solution. The discussion may have a .certain 

 popular interest from the fact that it is a type of many 

 problems in the structure and distribution of animals 

 and plants which seem to be associated with the laws of 

 evolution. In the light of these laws they may be more 

 or less perfectly solved. On any other hypothesis than 

 that of the derivation of species the solution of the 

 present problem, for example, would be impossible. On 

 the hypothesis of special creation a solution would be 

 not only impossible but inconceivable. 



It has been known for some years that in several 

 groups of fishes (wrasse fishes, flounders, and "rock 

 cod," for example) those species which 

 Northern fishes inhabit northern waters have more ver- 

 have most , , , ..... 



vertebra tebrse than those living in the tropics. 



Certain arctic flounders, for example, 

 have sixty vertebrae ; tropical flounders have, on the 

 average, thirty. The significance of this fact is the 

 problem at issue. In science it is assumed that all facts 

 have significance, else they would not exist. It becomes 

 necessary, then, to find out first just what the facts are 

 in this regard. 



221 



