MISCELLANEOUS ANIMALS 431 



havoc they may make in a garden or greenhouse. It is 

 interesting to watch their movements in gliding over the 

 glass. How do they do it ? Not like a leech or meas- 

 uring worm, by looping the body and holding on with first 

 one end, then with the other ; not like an earthworm, by 

 stretching the body and catching hold and drawing the rest 

 of the body up. But they remain apparently motionless, 

 neither longer nor shorter, and still glide smoothly and 

 rapidly along. They are nocturnal, feeding by night and 

 lying hidden in damp places during the day ; but a telltale 

 trail of slime is left wherever they go, and if they have 

 been doing mischief in the garden, they may easily be fol- 

 lowed home. The eggs are found under boards in damp 

 places, but instead of describing them I will ask the children 

 to find them, if they can, and keep them to make sure that 

 they hatch out into little slugs. The pupils may observe 

 how a slug eats, and they are sure to be interested in the 

 way it breathes, through a large hole, or spiracle, on 

 the right side. 



In order to keep the algae from overgrowing the sides of 

 our aquaria we need some snails, which the children can 

 find in any fresh- water pond or stream. The two kinds 

 that are most useful are represented in Fig. 174. Their 

 eggs are laid in glairy masses fastened to the water plants 

 or often to the glass where their development may be 

 easily watched. 



Among the bivalve mollusks are the oyster, clam, quahog, 

 scallop, and mussel, all valuable for food and connected 

 with interesting methods of cultivation and with fishery 

 industries. Where these can be studied alive, as along the 

 coast, they may be brought into the course. But the 



