26 PLANARIA NIGRA. 



ever seen of the largest size. One taken 

 in October was of light grey and. mottled, 

 or streaked with deeper transverse bands : 

 it was very broad in proportion to its length. 

 Yet it must be admitted, that repletion al- 

 ways affects the colour of the leading spe- 

 cies, which regularly darkens according to 

 age and increment. Probably, from disten- 

 sion of the vessels, shades of difference may 

 prevail, which temporary causes render 

 more prominent. 



The Black Planaria is endowed with 

 wonderful tenacity of life, a property which 

 materially aids the researches of the phy- 

 siologist. The truth is forcibly demonstra- 

 ted, by the dreadful lacerations with which 

 it appears in its natural element. Some- 

 times a large section from the neck is 

 wanting, sometimes a semicircular wound 

 almost divides the animal asunder, or one 

 half of the body has been tore from the 

 other, and still it survives the mutilation. 

 This was a sufficient guide. The genus had 

 been partitioned by nornenclators, according 



