5 
have agreed with them, but which now becomes 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 tigris, and the Panther is 
Felis concolor. The value of species has been admirably ex- 
pressed by Professor Huxley: — “Thus horses form a species, 
because the group of animals to which that name is applied is 
distinguished from all others in the world by the following 
constantly associated characters : — They have — i. A vertebral 
column; 2. Mammae; 3. A placental embryo; 4. Four 
legs; 5. A single well-developed toe on a foot provided with 
a hoof ; 6. A bushy tail ; and 7. Callosities on the inner side 
of both the fore and hind legs. The asses, again, form a dis- 
tinct species, because, with the same characters, as far as the 
fifth in the above list, all asses have tufted tails, and have cal- 
losities only on the inner side of the forelegs. If animals 
were discovered having all the general characters of the horse, 
but sometimes with callosities only on the forelegs, and more 
or less tufted tails, or animals having the general characters 
of the ass, but with more or less bushy tails, and sometimes 
with callosities on both pairs of legs, besides being interme- 
diate in other respects, the two species would have to be 
merged into one. They could no longer be regarded as 
morphologically distinct species, for they would not be dis- 
tinctly definable one from the other.” — Westminster Review, 
April, i860. 
