Q4t PLANARIA NIGRA. 



contracting into an elliptical spot, and then 

 affording the most favourable opportunity 

 for many being taken with facility at a time; 

 or they fix on the under surface of pieces 

 of slate and smooth stones somewhat ele- 

 vated above the mud. They live in nu- 

 merous pacific societies, associating with 

 every other species : and are so generally 

 dispersed, that none has occurred to me of 

 such frequency in Scotland. 



An animal so well known as the Black 

 Planaria scarce requires description ; nor, 

 considering its external uniformity of ap- 

 pearance, does there seem much room for 

 commentary. It is found of all different 

 sizes, from extreme minuteness to above 

 half an inch in length, and about an eighth 

 of an inch in breadth. When very large, 

 it has a dull and sluggish aspect, and is 

 chiefly roused to action by light and heat. 

 On the under part, or belly, are what natu- 

 ralists have designated two ventral pores, 

 one of which, — perhaps both, — is more con- 

 spicuous at certain seasons. The first is 



