STRUCTURAL RELATIONSHIP 



305 



Mammals 



Reptiles 



3000 



Amphibians 



700 



Arachnida 



4000 



Thread 

 Flat 



FIG. 107. Diagram showing the general relations of the chief divisions of 

 the animal kingdom. The number of species belonging to each is roughly 

 approximate only. (Galloway.) 

 20 



