VARIATION BY ENVIRONMENT. 
245 
selves. The English skylark is an illustration of this 
class. It was brought here, but perished because it 
could not maintain itself in the new environment. 
(3) Again, others having been introduced into a new 
environment, have been‘so changed by it that they 
Fig. 116.—Mud-puppy. 
are no longer 
recognized as the 
same species. 
For example, the 
European rabbit was taken to Porto Santo, one of 
the Madeira islands. It was able to maintain itself, 
but became so changed that it is now described as a 
new species. 
Islands in an ocean cut off from all continental 
influences have given us both flora and fauna pecul¬ 
iar because of the still existing antiquated types. The 
insects of such isolated islands are particularly inter¬ 
esting. 
The grasshoppers on the Cape Yerde islands are 
said to be almost wingless, not being able to use their 
17 
