EVOLUTION OP BIRDS. 15 



modified forms, is accepted by most naturalists. As 

 originally presented, it assumed that the continued exist- 

 ence of any animal depended upon its adaptation to its 

 manner of life. Among a large number of individuals 

 there is much variation in size, form, and color. Some 

 of these variations might prove favorable, others unfa- 

 vorable. Those which were favorable would give to the 

 individual possessing them an advantage over its fellows, 

 and, by what is termed Natural Selection, it would be 

 preserved and its favorable characters transmitted to its 

 descendants. But the less fortunate individuals, which 

 lacked the favorable variation, would be handicapped in 

 the race for life and be less likely to survive. 



Without necessarily opposing this theory, the follow- 

 ers of Darwin's predecessor, Lamarck, attach more im- 

 portance to the direct action of environment on the ani- 

 mal — that is, the influence of climate, food, and habit. 

 The effect of the first two I will speak of in treating of 

 color ; the last we may use to illustrate the difference in 

 these two theories by asking the question, " Is habit due 

 to structure, or is structure the result of habit ? " Has 

 ^Nature, acting through natural selection, preserved those 

 variations which would best fit a bird to occupy its 

 place in the world, and are its habits the outcome of 

 the characters thus acquired, or have the changes which 

 during the ages have occurred in a bird's home, forcing 

 it to alter its habits, been followed by some consequent 

 change in structure, the result of use or of disuse ? For 

 my part, I answer " Yes " to both questions, and turn to 

 our stiff-tailed, spear-tongued "Woodpecker to explain 

 my reply. I can readily understand how the shape of 

 these tail-feathers is the result of habit, for the same or 

 similar structure exists among many birds having no 

 close relationship to one another, but all of which agree 

 in their peculiar use of the tail as a prop ; the Creep- 



