^^ PLANARIA ARETHUSA. 



ments. It is of surprising length, being 

 little, if any, shorter Avhen fully extended 

 than the whole animal. Its contractility is 

 in proportion, which renders it susceptible 

 of diminution into its respective share, when 

 a voluntary reduction of its owner's size 

 ensues. If employed, it is either simply 

 cylindrical, flattened, or trumpet-shaped at 

 the extremity, as the planaria inclines ; and 

 when stretched to the uttermost, the root 

 becomes an apex of the slenderest cone. It 

 seems of greater consistency, harder, and 

 tougher than the rest of the body, so as to 

 admit insertion into decaying vegetables ; 

 but it is still of a gelatinous, and not of a 

 cartilaginous substance. Accordingly, the 

 leaves of plants, before becoming quite soft 

 and mucilaginous, may be seen studded 

 with punctures over the surface, proceed- 

 ing, as is probable, from the operation of 

 the proboscis. 



If this organ neither consists of rings nor 

 segments, and at the same time alternate- 

 ly lies in concealment within the body, and 



