HISTORY OF ZOOLOGY 



25 



preserved; the soft parts, which alone are present, or at least make up the 

 most important portions of many animals, are almost always lost. Only 

 rarely are they (muscle of fishes, ink-bag of cephalopods, outlines of 

 medusae) preserved in the rocks. Even the hard parts remain connected 

 only under exceptionally favorable conditions. If further we take into 

 consideration the fact that these treasures are buried in the earth, and are 

 usually obtained only by accident, in quarrying and road-building, it 

 becomes clear how little of the racial history is to be expected from 

 paleontology. 



mm 



IP- ji 



Fig. 2. Archaopteryx lilhographica (aitei Stemmann-Doderlein). c/, clavicle; co, 

 coracoid; h, humerus; r, radius; u, ulna; c, carpus; I-IV, digits; sc, scapula. 



Examples of Paleontological Proof. — Yet paleontology has already 

 furnished many important proofs of the theory of descent. It has shown 

 that the lower forms appeared first, and the more highly organized later. 

 Among animals in general the latest to appear were the vertebrates, and 



