DECEMBER 127 



Slugs are nocturnal lung-breathers, who do much 

 damage in gardens. The saddle is all that is left to 

 represent the mantle. There is an opening on the 

 right side which admits air. Underneath the mantle is 

 usually a small horny disk. 



Methods : 



How do the snails reach the top of the water ? How 

 often does Limnea come to the top ? Why ? 



^Miat does the snail eat ? How ? 



How does the snail move ? 



Distribute the empty shells. Let the children scrape 

 off the brown skin and test with strong vinegar the 

 shell beneath. The effervescence proves that it consists 

 of lime carlionate. 



AVhat good to the shell is the brown skin ? What has 

 happened to the tip where the skin has worn off ? 



With hektograph or blackboard drawings, teach the 

 parts of the animal. Land snails and slugs may be simi- 

 larly treated, or may be omitted, or taught by letting 

 the children read about them. 



^luSSELS. 



Facts : 



The mussels of the aquarium are really fresh-Avater 

 clams. 



The parts of the animal are sufficiently indicated in 

 the drawings on the next page. 



To the crawling action of the foot are due the long 

 tracks so often seen in the sand. 



The pearly lining of the shell is very beautiful and 

 one of the sources of domestic mother-of-pearl. 



The young of the mussel are stored away in the gill 



