22 Evolution and Adaptation 
OrGANS OF LITTLE USE TO THE INDIVIDUAL 
In every organism there are parts of the body whose 
presence cannot be of vital importance to the individual. 
We may leave out of consideration the reproductive organs, 
since their presence, as has just been stated, is connected 
with the continuation of the race. The rudimentary organs, 
so-called, furnish many examples of structures whose pres- 
ence may be of little or of no use to the individual; in fact, 
as in the case of the appendix in man, the organs may be a 
source of great danger to the individual. In this respect the 
organism is a structure not perfectly adapted to its conditions 
of life, since it contains within itself parts that are of little 
or of no use, which may even lead to its destruction, and may 
often expose it to unnecessary danger. Nevertheless such 
parts are surprisingly infrequent, and their presence is usu- 
ally accounted for on the supposition that in the past these 
organs have been of use, and have only secondarily come to 
play an insignificant part in the functions of the organism. 
Another example of the same thing is found in the rudi- 
mentary eyes of animals living in the dark, such as the mole 
and several cave animals, fishes, amphibia, and insects. 
There are still other organs, which cannot be looked upon 
as rudimentary, yet whose presence can scarcely be consid- 
ered as essential to the life of the individual. It is with this 
class that we are here chiefly concerned. For instance, the 
electric organs in some of the rays and fish can hardly 
protect the animal from enemies, even when as highly devel- 
oped as in the torpedo; and we do not know of any other 
essential service that they can perform. Whether the same 
may be also said of the phosphorescent organs of many 
animals is perhaps open in some cases to doubt, but there 
can be little question that the light produced by most of the 
small marine organisms, such as noctiluca, jellyfish, cteno- 
phores, copepods, pyrosoma, etc., cannot be of use to these 
