THE WONDEES OP THE SHOEE. 187 



to do, will sow tlieir minute spores in millions aronnd 

 them ; and these as they vegetate, will form a green 

 film on the inside of the glass, spoiling yonr prospect ; 

 you may rub it off for yourself, if you wiU, with a 

 rag fastened to a stick, but if you wish at once to 

 save yourself trouble, and to see how all emergencies 

 in nature are provided for, you will set three or four 

 live shells to do it for you, and to keep your sub- 

 aqueous lawn close mown. 



That last word is no figure of speech. Look among 

 the beds of sea-weed for a few of the bright yellow 

 or green sea-snails (Nerita), or Conical Tops (Trochus), 

 especially that beautiful pink one spotted mth brown 

 (Ziziphinus), which you are sure to find about shaded 

 rock-ledges at dead low tide, and put them into your 

 aquarium. For the present, they will only nibble 

 the green ulvse, but when the film of young weed 

 begins to form, you will see it mown off every morn- 

 ing as fast as it grows, in little semicircular sweeps, 

 just as if a fairy's scythe had been at work during 

 the night. 



And a scythe has been at work; none other than 



