234 
HAROLD’S DISCUSSIONS. 
One species often grades into another; hence sub¬ 
species and subvarieties have been used to designate 
more definitely intermediate forms. 
Families include one or more related genera. The 
dog family embraces the genera Canis^ Lupus, and 
Yulpes. A number of families constitute an order, 
as the carnivora include all the fiesh-eaters—dogs, 
cats, wolves, foxes. Suborders, tribes, and subfami¬ 
lies are also employed to designate intergrading va¬ 
riations. 
Recent studies have shown that there is no signifi¬ 
cant break that would divide animals or plants into 
definite groups, as the classifications might suggest, 
but the grouping is still retained because of its con¬ 
venience. 
