140 LIFE AND HER CHILDREN. 
tribe. These are the so-called " tape-worms " which 
can only grow to their full strength in warm-blooded 
animals, and are armed with both hooks and suckers 
on the head. Now, while the front part of this head 
is firmly fixed, buds are given off continually from 
the other end, making a long tail with many joints, 
each of which carries eggs, and often has its own 
separate suckers and hooks to hold firmly to its host. 
These creatures have no mouths or stomachs, but 
take in the fluid food all over their body as it passes 
by them on its way through the animal they inhabit 
Tape-worms wander just as flukes do, thus the tape- 
worm of the dog begins its life in the sheep, that of 
the cat lives first in the mouse, that of the fox in the 
hare or rabbit, that of the water-bird in the fish. 
Nor is it only flat -worms which have become 
parasites ; the little wriggling round worms live, many 
of them, in the grubs of beetles and insects, and from 
these pass on into the bodies of rats and mice, 
squirrels and birds, or fishes. The little thread-worm 
Mermis, for example, as soon as it is hatched in the 
moist earth in spring time, uses a sharp dagger 
hidden in its head to pierce a road for itself into the 
body of a grub, and lives upon its juices till either 
the caterpillar becomes a butterfly, or is eaten, or 
the mermis is ready to lay her eggs, and then she 
pierces her way out again to lay her young in the 
soft earth. 
Another little round worm hangs on by its suckers 
inside the throat of the chicken, giving it the " gapes," 
which can be cured if the worm is brushed out with 
a feather ; while the Trichina so dangerous in half- 
raw pork or ham, is another round worm, living ir 
