140 SPECIES AND BREEDS. 
combined under a definite pattern of form which 
characterizes its Family, — that every individual 
exhibits structural details in the finish of its parts 
which characterize its Genus, —and finally that 
every individual presents certain peculiarities in 
the proportion of its parts, in its.color, in its size, 
in its relations to its fellow-beings and the sur- 
rounding objects, which constitute its specific 
characters; and all this is repeated in the same 
kind of combination, generation after generation, 
while the individuals themselves die. If we ac- 
cept these propositions, which seem to me self- 
evident, it is impossible to avoid the conclusion 
that Species do not exist in Nature in any other 
sense than the more comprehensive groups of the 
zoological system. 
There is one question respecting Species that 
gives rise to very earnest discussions in our day, 
not only among naturalists, but among all 
thinking people. How far are they permanent, 
and how far mutable? With reference to the 
permanence of Species, there is much to be 
learned from the geological phenomena belong- 
ing to our own period, in as far as they bear 
witness to the invariability of types during hun- 
dreds of thousands of years at least. I hope to 
present a part of this evidence in a future article 
upon Coral Reefs, but in the mean time I cannot 
leave this subject without touching upon a point 
