II ON ANIMAL LIFE 45 
RUDIMENTARY ORGANS 
Such modifications may be called adaptive, 
but there are others of a different origin 
that have reference to the changes which 
the race has passed through in bygone ages. 
In fact the great majority of animals do go 
_ through metamorphoses (many of them as 
remarkable, though not so familiar as those 
of insects), but im many cases they are passed 
through within the egg and thus escape 
popular observation. Naturalists who accept 
the theory of evolution, consider that the 
development of each individual represents to 
a certain extent that which the species has 
itself gone through in the lapse of ages; that 
every individual contains within itself, so to 
say, a history of the race. Thus the rudi- 
- mentary teeth of Cows, Sheep, Whales, etc. 
(which never emerge from their sockets), the 
rudimentary toes of many mammals, the hind 
legs of Whales and of the Boa-constrictor, 
which are imbedded in the flesh, the rudi- 
mentary collar-bone of the Dog, etc., are in- 
