458 
SUMMARY. 
Chap. XIIL 
organs, though fitted in the adult members for pur¬ 
poses as different as possible. Larvae are active em¬ 
bryos, which have become specially modified in relation 
to their habits of life, through the principle of modifica¬ 
tions being inherited at corresponding ages. On this 
same principle—^and bearing in mind, that when organs 
are reduced in size, either from disuse or selection, it 
will generally be at that period of life when the being 
has to provide for its own wants, and bearing in mind 
how strong is the principle of inheritance—the occur¬ 
rence of rudimentary organs and their final abortion, 
present to us no inexplicable difficulties; on the con¬ 
trary, their presence might have been even anticipated. 
The importance of embryological characters and of 
rudimentary organs in classification is intelligible, on 
the view that an arrangement is only so far natural as 
it is genealogical. 
Finally, the several classes of facts which have been 
considered in this chapter, seem to me to proclaim 
so plainly, that the inumerable species, genera, and 
families of organic beings, with which this world is 
peopled, have all descended, each within its own class 
or group, from common parents, and have all been 
modified in the course of descent, that I should without 
hesitation adopt this view, even if it were unsupported 
by other facts or arguments. 
