VESTIGIAL PARTS. 61 
convenience of employing the term vestigial ; there can 
be little doubt that its hind limbs are remnants. 
The combined effects of enlargement from increased 
use, suppression, and change of function, has been to 
produce in complex organisms a large number of ves- 
tigial parts. Since Darwin considered the matter our 
knowledge of such parts has increased greatly, and 
in this chapter a few of the more important will be 
considered, especially those which lead to pernicious 
consequences. 
Before entering upon this subject in detail it is neces- 
sary to make a few remarks on what are termed wseless 
parts. It is very essential that care be exercised before 
pronouncing any part to be useless, for, as Mr. Wallace 
truly remarks, “ much of what we suppose to be useless 
is due to our ignorance.” It also becomes important 
to inquire why such supposed useless organs are per- 
petuated, seeing that disuse of a part tends to promote 
its disappearance. Darwin was of opinion that what 
he termed “rudimentary organs are eminently variable, 
and this is intelligible, as they are useless, or nearly 
useless, and consequently no longer subjected to natural 
selection. They often become wholly suppressed. When 
this occurs they are nevertheless liable to occasional 
reappearance through reversion.” Subsequently Darwin 
seems to have changed his opinion somewhat, for in the 
fifth edition of the “Origin of Species” he states, in 
reference to adaptive changes of structure, “But I am 
convinced from the light gained during even the last 
few years that very many structures which now appear 
to us useless will hereafter be proved to be useful and 
