228 THE BOOK OF A NATURALIST 
velvety-black back became visible, and made in 
its setting of red and yellow leaves a prettily 
coloured picture. Presently he disappeared, then 
quickly rose again with more earth; but the 
leaves evidently annoyed him, and to rid himself 
of them he suddenly began agitating his body in 
an astonishing way, for while the movement lasted 
he looked like a black ball spinning round so rapidly 
as to give it the misty appearance of a revolving 
wheel or the wings of a hovering hawk-moth. 
This swift motion on his part set the leaves flying, 
and mole and dust and dancing leaves together 
formed a little whirlwind or maelstrom. When 
it was over the leaves settled again on the mound, 
and twice again the extraordinary performance was 
repeated, and the little animal being then almost 
above the ground I foolishly put out my hand to 
pick him up, and before I could properly grasp him 
he was gone. 
The spinning or revolving motion was an illusion 
of the sight produced by the exceedingly rapid 
motions of the skin while the animal was stationary, 
and the deluding motions were effected by means 
of what the anatomists call the “twitching muscle,” 
which is possessed in some degree by most, if not 
by all, mammalians. We see it every day in our 
domestic animals, especially in the dog when he 
shakes himself after a swim; and if he has shaggy 
hair and it is full of water he throws it off so 
violently that it fills the air with a dense spray 
for several feet around him. He could not do this 
