LATITUDE AND VERTEBRA. 



225 



In my view the reduction in number and increase of 

 importance of the individual vertebrae are simply part 

 of a process we may call ichthyization, the work of 

 making a better fish. Not a better fish for man's pur- 

 poses — for Nature does not care for man's purposes — 

 but a better fish for the purposes of a fish. The com- 

 petition in the struggle for existence is the essential 

 cause of the change. In the centre of competition no 

 species can afford to be handicapped by a weak back- 



FlG. 18. — Skeleton of angel fish {Angelichthys ciliaris). From nature, 

 by W. S. Atkinson. A tropical species ; the vertebrae few and 

 large. 



bone and redundant vertebrae. Those who are thus 

 weighted can not hold their own. They must change or 

 perish. 



The influence of cold, darkness, monotony, and iso- 

 lation is to limit the struggle for existence, and there- 

 fore to prevent its changes, preserving 

 Coral reefs the .1 ^^ .^ ■ , , ,. , 



centre of fish through the conservation of heredity the 



competition. more remote ancestral conditions, even 



though they carry with them disadvan- 

 tages and deficiencies. The conditions most favourable 

 to fish life are among the rocks and reefs of the tropical 

 seas. About the coral reefs is the centre of fish compe- 

 tition. A coral archipelago is the Paris of fishes. In 

 such regions is the greatest variety of surroundings, and 



