456 
SUMMARY. 
Chap. XIII. 
reason to believe to be possible), the rudimentary part 
would tend to be wholly lost, and we should have a case 
of complete abortion. The principle, also, of economy, 
explained in a former chapter, by which the materials 
forming any part or structure, if not useful to the pos¬ 
sessor, will be saved as far as is possible, will probably 
often come into play; and this will tend to cause the 
entire obliteration of a rudimentary organ. 
As the presence of rudimentary organs is thus 
due to the tendency in every part of the organisation, 
which has long existed, to be inherited—we can under¬ 
stand, on the genealogical view of classification, how it is 
that systematists have found rudimentary parts as useful 
as, or even sometimes more useful than, parts of high 
physiological importance. Rudimentary organs may be 
compared with the letters in a word, still retained in 
the spelling, but become useless in the pronunciation, 
but which serve as a clue in seeking for its derivation. 
On the view of descent with modification, we may con¬ 
clude that the existence of organs in a rudimentary, 
imperfect, and useless condition, or quite aborted, far 
from presenting a strange difficulty, as they assuredly 
do on the ordinary doctrine of creation, might even 
have been anticipated, and can be accounted for by the 
laws of inheritance. 
Summary ,—In this chapter I have attempted to show, 
that the subordination of group to group in all organisms 
throughout all time; that the nature of the relationship, 
by which all living and extinct beings are united by 
complex, radiating, and circuitous lines of affinities into 
one grand system; the rules followed and the difficulties 
encountered by naturalists in their classifications; the 
value set upon characters, if constant and prevalent, 
whether of high vital importance, or of the most trifling 
