LATITUDE AND VERTEBR&. 225 
In my view the reduction in number and increase of 
importance of the individual vertebre are simply part 
of a process we may call ichthyization, the work of 
making a better fish, Nota 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- 
Fic. 18.—Skeleton of angel fish (Angelichthys ciliaris). From nature, 
by W. S. Atkinson. A tropical species; the vertebrae few and 
large. 
bone and redundant vertebre. 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 
through the conservation of heredity the 
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 Pars of fishes. In 
such regions is the greatest variety of surroundings, and 
Coral reefs the 
centre of fish 
competition. 
