THE WORMS : 
FEXHE worms include a large number of creatures which differ 
greatly one from another, both in form and in habits of life. 
They are found in almost every imaginable situation, although 
generally dependent upon moisture for their development. Many 
sorts of worms are parasites, and no animal is wholly free from 
their attacks. 
Although repulsive at first sight, worms are really among the 
most interesting of all animals, for a careful study of their develop- 
ment and structure shows that crustaceans, insects and mollusks are 
probably descended from worm-like ancestors. 
The flatworms or Platodes are among the simplest of all worms. 
The free-swimming flatworms are common upon seaweed-covered 
rocks, or upon dead shells. They are generally small creatures 
more or less leaf-shaped with the front end of the body bluntly 
rounded. They crawl or swim with a wave-like motion. The sucker- 
like mouth is upon the lower surface, never at the extreme front of 
the creature; and the intestine ends blindly, so that undigested 
particles of food are cast out through the mouth. Numerous little 
eye-spots and sensory hairs are often seen on the upper surface of 
the worm, and the nervous system is well developed. The brain is 
near the front end, and gives rise to two main nerve branches which 
extend down the body near the lower surface and are joined at regu- 
lar intervals by cross fibres, making a ladder-like arrangement. 
The flatworms often lay their eggs in cocoons or capsules, each cap- 
sule containing a considerable number of eggs, only a few of which 
develop; the remainder being devoured by the successful larvee. 
The tapeworms and flukes are related to the flatworms, and are 
parasitic within many animals. The development of these para- 
sites is interesting, for example the tapeworm produces eggs which 
develop into little embryos, each with four or six hooks and suckers, 
and which are then cast out and die, unless accidentally swallowed 
by some other animal. In this event, however, the little tapeworm 
gets rid of its egg-shell, and bores its way through the wall 
