Origin of Different Kinds of Adaptations 355 
The most obvious interpretation is that the degeneration has 
been the result of disuse. But as I have already discussed 
this question, and given my reasons for regarding it as im- 
probable that degeneration has arisen in this way, we need 
not further consider this point here. 
The selectionists have offered several suggestions to 
account for degeneration. In fact, this has been one of the 
difficulties that has given them most concern. They have 
suggested, for example, that when an organ is no longer of 
use to its possessor it would become a source of danger, 
and hence would be removed through natural selection. 
They have also suggested that since such organs draw on the 
general food supply they would place their possessor at a 
disadvantage, and hence would be removed. Weismann has 
attempted to meet the difficulty by his theory of “ Panmixia,” 
or universal crossing, by which means the useless structures 
are imagined to be eliminated. 
These attempts will suffice to point out the straits to 
which the Darwinians have found themselves reduced, and 
we have by no means exhausted the list of suggestions that 
have been made. Let us see, if, on any other view, we can 
avoid some of the difficulties that ‘the selection theory has 
encountered. 
In the first place we shall be justified, I think, in eliminat- 
ing competition as a factor in the process, since the admis- 
sion that an organ has become useless carries with it the 
idea that it has no longer a selective value. If, in its useless 
condition, it is no longer greatly injurious, as is probably, 
though not necessarily always, the case, then selection can- 
not enter into the problem. If in parasitism we assume that 
an animal finds a lodgement in another animal, where it is 
able to exist, we may have the first stage of the process 
introduced at once. If under these conditions a mutation 
appeared, involving some of the organs that are no longer 
essential to the life of the individual in its new environment, 
