
264 STUDY OF NATURAL HISTORY. 
the humming-birds, the sun-birds, the whole of the 
typical waders (Grallatores), the Lepidoptera and 
Hemiptera, the zoophagous Testacea, the suctorial 
Radiata, the worms and the leeches. These ex- 
amples, it will be perceived, are taken almost’ at 
random from different classes of the animal king- 
dom; and clearly show that essential characters, 
founded on this particular structure, are of primary 
consequence. 
(182.) We are now to consider the value of 
distinctions derived from the organs of locomotion, 
that is, from the feet and wings: these two members 
being represented in fish and other aquatic animals 
by jins. Each of these is entitled to a separate 
consideration. The most perfect developement of 
foot is found in quadrupeds, and the different modi- 
fications of structure which it presents are truly 
surprising: the feet of some are barely sufficient to 
enable the animal to crawl slowly and irregularly 
upon the ground; and even this, in the sloths, is 
obviously accompanied with pain. Some of the 
Lemurs, also, are equally incapacitated from the 
ordinary motion of quadrupeds. Yet, place these 
animals on trees, and they appear to be in their 
proper element — active, expert, and indefatigable ; 
‘they live, and move, and have their being,’ not 
by walking but by climbing. But the most accom- 
plished scalers of trees are the monkeys, whose 
limbs, in fact, are more perfectly formed for this 
purpose than those of any quadruped in creation : the 
agility which th®se animals display in their native 
forests is really astonishing, and far exceeds that 
which they still retain in confinement. What a con- 
