CREATION BY EVOLUTION 



In this account of the origin of the birds I have dealt only 

 with certain selected parts of the body, and with only a few 

 of the changes in the conditions of life. For example, I have 

 not referred to the modifications of structure that are needed 

 to enable a bird to perch on a twig. The features that I 

 have mentioned were selected because they can be explained 

 without presenting too much detail, and because they show 

 the retention in birds of features whose presence is due to 

 their existence as useful modifications of like features in 

 their reptilian ancestors. The points considered may be 

 summarized as follows: 



1. The bird owes the presence of two, three, four, or five 

 phalanges, or joints, in its toes to the fact that its reptilian 

 ancestor, owing to its straddling gait, required toes that 

 increased in length from the first to the fourth, whereas in 

 the bird the second toe, which has three phalanges, and the 

 fourth toe, which has five, are actually of the same length. 



2. The bird owes the anomalous manner in which its 

 aorta crosses from the left to the right side of the center of 

 the body to the fact that in reptiles only this one of the pair 

 of aortae transmits pure blood. 



3. The bird owes its possession of only the first three fin- 

 gers and not, as might have been expected, the fourth and 

 fifth fingers, to the fact that the first three fingers are those 

 which are most useful in the reptilian ancestor for clasping 

 food between the two hands. 



4. The bird owes the character of its brain to its descent 

 from an animal having a brain like a crocodile. 



This list might be extended indefinitely, but these four 

 examples are sufficient to show that the peculiarities of the 

 bird's structure — the points in which it seems to be clumsily 

 constructed — are at once explained as relics derived from its 

 reptilian ancestor. 



[250] 



