PLANARIA NIGRA. 35 



low waters, affording an insecure retreat 

 from the rigour of the atmosphere ; nor are 

 they diminished in succeeding seasons. 

 The bodies of those which perish thus, are 

 distorted, stiff, and invested by a very thick 

 coating of gluten. In a few hours after so- 

 lution of the ice, they become soft and re- 

 laxed, and are quickly decomposed. 



Monstrosities sometimes occur in the 

 black planaria, and frequent distortions from 

 casual injury. In 1808, one was found 

 with the tail bifid ; a ventral pore appeared 

 in each portion, both of which might be 

 considered members of the same body. 

 Accident may give birth to superfluous 

 parts, as well as the skill of the experimen- 

 talist ; but this species, perhaps from the 

 energy of its reproductive powers, seems 

 less adapted for acquiring them. 



In addition to what has been said of va- 

 rieties, we may observe, that a few are ta- 

 ken in places inhabited by the black plana- 

 ria, of smaller size, the head rather more 

 obtuse, and the tail suddenly drawing to- 



