CHAPTER XIX 

 CLASSIFICATION AND DISTRIBUTION 



EVEN the slightest familiarity with organisms will disclose 

 striking similarities between some forms and great differences 

 between others. The frog is clearly quite like the lizard and 

 much like other vertebrates, but very unlike the earthworm. 

 These points of likeness are the basis upon which organisms are 

 classified. 



il 



mt tar 



FIG. 145. THE SKELETON OP A RABBIT 



c, carpals; 

 /, fibula ; 

 fe, femur; 

 h, humerus; 



il, ilium; 

 is, ischium; 

 me, metacarpals; 

 mt, metatarsals; 



pu, pubis; 

 tar, tarsala; 

 r, radius; 

 sc, scapula; 



at, sternum; 

 t, tibia; 

 u, ulna. 



Homology. The likeness between organisms is of two general 

 types. The first is likeness in structure, which is called homology 

 (Gr. homos = like + logos = ratio) . It is frequently found that 



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