38 LESSON V 



many more equally beautiful contrivances, a 

 breach is often effected in the habitation of the 

 mollusca, 



Child. And then the poor animals must 

 perish ] 



Teacher. This is by no means inevitably the 

 case, for they are gifted with the power of repair- 

 ing their shells. 



Child. How do they manage this ? 



Teacher. By a discharge of the same cal- 

 careous matter, of which they at first constructed 

 their shells. You might by your own expe- 

 rience prove that this is true. You should pro- 

 cure in the spring some common snails, break 

 off a part of their shells, then giving them a sup- 

 ply of food, place them under a glass that you 

 may watch their operations. You would ob- 

 serve first a frothy matter exuding from that part 

 of the animal you had uncovered and forming a 

 film, in a short time a second discharge would 

 raise the first to the level of the external surface 

 of the shell, and by degrees fresh accessions 

 would give the new part the thickness and sub- 

 stance of the old shell. 



Child. It would be very amusing to watch 

 this experiment. 



Teacher. But do you not admire the instinct 

 that so wonderfully directs these little animals 

 in their self-preservation ? 



Child. It is very surprising, certainly, that 

 such a worm should have the power of remedying 

 so great disasters. But could not God have 

 enabled them to form their shell at first too strong 



