84 
SYSTEM OF NATURE. 
be convinced of the total want of identity between the eye 
or wing of a butterfly and the eye or wing of a swallow : 
if we attempt to separate the component parts of these in¬ 
struments, and to subject them to an uniform anatomical 
nomenclature, we shall find the task utterly impracticable. 
On the contrary, if we dissect the eye or arm of a man, 
we shall be able to trace most of its component parts in a 
bird, a kangaroo, a lizard, a tortoise, a perch, or a shark ; 
or if we dissect the leg of a butterfly, we shall be able to 
trace its component parts in the leg of a gnat, a bee, a 
beetle, a grasshopper, a cicada or a dragon-fly. 
Still do I consider the end far greater than the means; 
the faculty more important than the machinery by which it 
is obtained; the propensity of greater consequence than the 
structure through whose instrumentality it is gratified. It 
appears to me that a correspondence in some well marked 
character in the mode of life, — such for instance as rapid 
and unwearying flight or the total inability to fly; rapidity 
or slowness of terrestrial progression ; great power of 
swimming and inability to leave the water or the propen¬ 
sity to shun it altogether; savage unrelenting ferocity and 
thirst for blood or the inability to appropriate any other 
than vegetable food; gluttonous and insatiable appetite 
or the power of total abstinence; perfect and quick respi¬ 
ration or the power of suspending this function for an al¬ 
most indefinite period;—• should be regarded as of greater 
importance, and as offering analogies of far higher value, 
than those metaphorical and often imaginary similarities of 
structure to which such overwhelming importance has 
hitherto been attached. Real co7°respondence in structure 
stands quite preeminent, and when we lose sight of this, 
when we abandon the group bound together by this real 
