NUTRITION 43 



unimportant in the physiology oi Hirudo and van Emden (1929) 

 thought that fat was actively excreted. The marked difference 

 between the two types of metabolism may be related to the differ- 

 ences in diet. While Hirudo is purely sanguivorous Glossiphonia 

 plunges its proboscis into the tissues of a freshwater snail and after 

 removing the liquids it may finally suck all the soft parts out of 

 the shell. 



