108 ANIMAL ACTIVITIES. 
Compare the eyes in the three animals. 
The Importance of Homologies. We have already 
pointed out the fact that parts may be homologous and 
Fic. 94.—The Common Crab. 
yet appear very unlike. Parts which arise in the same 
way in the processes of development may become so 
Fic. 95.—Early Stages of Shore-crab. 
variously modified that their real homologies could not 
be known without a study of embryology. Hence it 
