32 DROPS OF WATER. 



the skin, as in many kinds mouths could not be 

 discovered ; but by feeding them on coloured 

 substances, an internal structure has been ob- 

 served equally complicated with that of larger 

 animals, and consisting of muscular and nervous 

 systems, all wonderfully suited to their respective 

 wants. As these creatures are for the most part 

 transparent, the being enabled to feed them on 

 coloured substances, such as indigo, sap-green, 

 and carmine, has given naturalists the power of 

 investigating the internal construction, which 

 would have been impossible without this plan. 

 The method is to place a very small portion of 

 the carmine, well rubbed down with a little 

 water, in a drop containing animalcules ; they 

 will immediately appear very active, and in a 



