78 The Insides and the Workings of Living Things 



Flans of Structure 



The difficulties of the earliest students of classification 

 grew in a measure from the failure to recognize these differ- 

 ent plans. To arrive at this much insight, it was first nec- 

 essary to do a great deal of comparing, of critical checking 

 of details of structure. One of the first attempts to compare 

 in detail the structure of one type of animal with that of 

 another was made three hundred years before Darwin pub- 



FiG. 15. Misleading Resemblances 



The general appearance or form of a living thing may furnish a misleading 

 resemblance to one of a different class. The mountain lizard, Lacerta vivipara, 

 is a reptile, related to snakes and turtles, whereas the newt, Ambystoma 

 maculatum, is an amphibian, related to frogs and toads. 



lished his Origin of SpecieSy when the French naturalist, 

 Pierre Belon, published comparative descriptions and pictures 

 of many animals, and studied especially the bones of birds 

 and of man in corresponding postures. Over two hundred 

 years later a French court physician and anatomist, Vicq 

 D'Azyr, made a more detailed comparison of the limbs of 

 quadrupeds and of man, showing especially the precise cor- 

 respondence between the more important muscles of the 

 arms and legs. He made also the most detailed study of 

 the structure of the brain up to his time, and an extensive 



