ADDITIONAL FACTS ABOUT MYRIAPODS. 67 



This enables us to understand more clearly what 

 is meant by homology, and to explain why we count 

 one body segment in the head for each pair of paired 

 appendages, and so determine that the body of the 

 grasshopper is composed of seventeen body segments. 

 This also enables us to explain why the mandibles of 

 the grasshopper move sideways. The appendages are 

 paired on each segment, and so are brought to oppose 

 each other, just as the two hands of a man together 

 seize upon an object to hold it or to lift it up. 



To the Teacher. 



The utility of the study of homology is to train the mind to 

 perceive logical identity. The homology of the maxillipeds and 

 the demonstration of the identity of the jaws of a grasshopper with 

 the legs is an important lesson, and should be carefully prepared 

 and worked out. 



