222 FOOT-NOTES TO EVOLUTION. 
Going through the various groups of non-migratory 
marine fishes we find that such relations are common. 
In almost every group the number of vertebre grows 
smaller as we approach the equator, and grows larger 
again as we pass into southern latitudes. 
It would be tedious to show this here by statistical 
tables, but the value of generalization in science de- 
pends on such evidence. This proof I have elsewhere * 
given in detail. Suffice it to say that, taking an average 
netful of fishes of different kinds at different places 
along the coast, the variation would be evident. At 
Point Barrow or Cape Farewell or North Cape a seine- 
ful of fishes would perhaps average eighty vertebrae 
each, the body lengthened to make room for them; at 
Sitka or St. Johns or Bergen, perhaps, sixty vertebre; 
at San Francisco or New York or St. Malo, thirty-five; 
at Mazatlan or Pensacola or Naples, twenty-eight; and 
at Panama or Havana or Sierra Leone, twenty-five. 
Under the equator the usual number of vertebrz in 
shore fishes is twenty-four. Outside the tropics this 
number is the exception. North of Cape Cod it is virtu- 
ally unknown. 
The next question which arises is whether we can 
find other conditions that may affect these numbers. 
These readily appear. Fresh-water fishes 
have in general more vertebrz than salt- 
water fishes of the same group. Deep- 
sea fishes have more vertebre than fishes 
of shallow waters. Pelagic fishes and free-swimming 
fishes have more than those which live along the shores, 
Fewest vertebre 
in shore fishes of 
the tropics. 
* In a more technical paper on this subject entitled Relations 
of Temperature to Vertebree among Fishes, published in the Pro- 
ceedings of the United States National Museum for 1891, pp. 107- 
120. Still fuller details are given in a paper contained in the 
Wilder Quarter-Century Book, 1893. 
