PUZZLES AND PATRIARCHS. 193 



This sub-division of the fishes is the result of 

 a careful analysis of all the characteristics of the 

 class, and has brought us not only somewhere 

 near the extreme base of the piscine branch of 

 the great vertebrate tribe, but it has also marked 

 out the lines along which our investigation into 

 the descent of the various smaller groups must 

 proceed, if we would know more of the evolution 

 of fishes. 



CHAPTER XIY. 



PUZZLES AND PATRIARCHS. 



MOST of Nature's children are, so to speak, " ear- 

 marked," so that those who will take the trouble 

 to learn the nature of these marks may tell 

 thereby to what great branch of the animal 

 kingdom any particular individual belongs. 

 Those who are skilled in the interpretation of 

 these marks can go further, they can tell not 

 only to what tribe it belongs, but what position 

 it holds in that tribe. 



Sometimes just one mark alone is of sufficient 

 importance to enable us to dispense with all 

 others. Birds afford us an admirable instance of 

 this. We can distinguish a bird at once from 

 all other known animals by the fact that it pos- 

 sesses feathers. Feathers form the external 

 covering of the bird, and are absolutely unique 

 structures, being produced by no other animal 

 under the sun. Now fishes are by no means 

 so distinctly and decidedly marked. Generally 



