188 THE HAUNTS OF LIFE 
waves of sound strike; this is the door at which 
they knock. But the vibrations have to be 
conveyed to the real ear—the delicate organ of 
hearing—which is safely lodged in very dense 
bone (periotic) deeper down in the skull. Now, 
running from the drum of the ear to the inner 
ear, there is, in mammals, a chain of three 
little bones called the Hammer, the Anvil, 
and the Stirrup (Malleus, Incus, and Stapes). 
What do these turn out to be? Their develop- 
ment shows that they are just transformed 
pieces of bone which, in fishes, form part of 
the commonplace framework of the jaws. 
This is another tell-tale evidence of the very 
distant aquatic ancestry of mammals. 
Another very remarkable fact has to do 
with the blood. Many of the lower animals, 
such as sponges and jelly-fishes, sea-anemones 
and corals, and the simpler worms, have no 
blood; but every one knows that this is very 
unusual. From ringed worms to man, almost 
all animals have blood, though, in many cases, 
like lobster and snail, it is not very noticeable, 
being practically colourless. This blood is a 
very complex, chemical mixture; its watery 
basis contains solutions of salts, sugar, pro- 
teins, and nitrogenous waste-products. Every 
