174 FIRST BOOK OF ZOOLOGY. 



With the exception of the fishes, tlie similarity in the 

 character and arrangement of the bones of the skeleton of 

 every vertebrate is remarkable. Even the birds, which are 

 apparently so different from the mammalia on the one hand 

 and the tm-tle and salamander on the other, are yet quite 

 similar to each in the general character and arrangement 

 of their bones ; and if the young bird, while yet in the egg, 

 is examined, the presence and affinities of certain bones are 

 very clearly seen. 



CHAPTER XXIII. 



BONES OF THE LEG AKD WIXG OF BIEDS. 



156. OuE pupils have learned by this time how impor- 

 tant it is to study the very young animal in order to deter- 

 mine its relationships. Thus in studying the young barna- 

 cle the affinities of the creature were more readily recog- 

 nized, and in the affinities of the parts of the animal, by 

 studying the young spider the palpi were more easily seen to 

 be modified legs. Now, as an interesting example of the 

 necessity of studying the young or early condition of an 

 animal, a bird is cited. 



The fore-leg in the bird is represented by its wing, and 

 in studying the bones of the wing of an adult bird but little 

 resemblance can be seen between them and similar parts in 

 other vertebrates. The humerus, radius, and ulna are plain 

 enough, it is true, and, when the pupil has a chance to pick 



