ONTOGENY 261 



homologous, by which is meant that they conform to a general 

 structural type because they were differentiated by evolution 

 from the same or corresponding part of an ancestral organism. 

 Similarity of development of parts is taken as an indication of 

 similarity in origin. Analogy refers to similarity in function. 

 The wings of a bird and the arms of a man are homologous but 

 not analogous ; the eyes of a squid and those of man are analogous 

 but not homologous; while the arms of an ape and the arms of 

 man are both homologous and analogous. 



