Then he brings forth a family--of tiny worms quite unlike himself, little creatures called _rediae_, which soon give birth to families of young _rediae_.

So they may go on for several generations, but at last there comes a generation of _rediae_ which, instead of giving birth to fresh _rediae_, produce families of totally different offspring; big-headed, long-tailed creatures like miniature tadpoles, called by the learned _cercariae_.

The _cercariae_ soon wriggle their way out of the body of the snail, and then complications arise: for it is the habit of this particular snail to leave the water occasionally and take a stroll in the fields.

Thus the _cercariae_, escaping from the snail, find themselves on the grass, whereupon they promptly drop their tails and stick themselves to the grass-blades.

Then comes the unsuspecting sheep to take his frugal meal, and, cropping the grass, swallows it, _cercariae_ and all.