4 
nearness with which they approach to one of the five great 
types of structure which have been found to exist among 
them:— 
I. Mammalia —animals which suckle their young. 
II. Aves, or birds. 
III. Batrachia —as frogs, toads, and salamanders. 
IV. Reptilia —as turtles, lizards, and serpents. 
V. Pisces , or fishes. 
These classes are again broken up into orders , each posses¬ 
sing an association of structural characters which is common 
to all the individuals included in it, and in which they differ 
from all other individuals in their class. These orders have 
been differently constituted and arranged, according as differ¬ 
ent points have been made use of for their determination. 
They are again divided into smaller groups called families , 
which, possessing the characteristic mark of their order , yet 
depart in some minor consideration from its type—or, in 
other words, from that form which has been taken to show 
most clearly the peculiarity of the order. 
Families are again broken up into genera , which bear to 
them much the same relation as that which they, in turn, 
bear to orders. Thus—to illustrate with a familiar example— 
the lion, tiger, panther, &c., are all cats and belong to one 
genus— Felis; they are classified as follows :— 
Division Vertebrata —because they have a backbone or ver¬ 
tebral column. 
Class Mammalia —because they have organs peculiar to 
those animals which suckle their young. 
Order Carnivora —because their plan of structure is that 
possessed by mammals which live on flesh. 
Family Felidae —because, in addition to the above, they 
possess a common arrangement of teeth, claws, and other 
structural points, which none of the other carnivora share. 
Genus Felis —because certain minor modifications are un¬ 
like those existing in a few more individuals, which so far 
have agreed with them, but which now become another 
genus of the same family. 
But to go a step farther—the lion, tiger, and panther, 
though so far they have been precisely similar, are yet recog¬ 
nizable—there are still smaller points of difference ; they are, 
therefore, said to be different species , and a second name is 
added to the scientific designation of their genus; thus the 
Lion is Felis leo , the Tiger is Felis ligris, and the Panther is 
Felis concolor . 
