10 PLANARIA FLEXILIS. 



minishes with the approach of cold. Thus, 

 the specimens delineated in the annexed 

 Engravings are not of the extreme dimen- 

 sions, which may unquestionably be aug- 

 mented by a copious and regular supply of 

 aliment, independent of the temporary in- 

 crement attained. Temperature and food 

 must always be taken into account, in 

 speaking of size, for both contribute to en- 

 large the contour of the body. Besides, it 

 essentially merits consideration, that the 

 colour of the entire animal is principally 

 regulated by the tinge of the aliment re- 

 ceived ; and if we say it is naturally of a 

 dull white, this means in a state of absti- 

 nence. Its proper abode, however, being 

 among mud, that substance promotes a 

 tawny hue ; for, on removal from it, pla- 

 nariae become much clearer, and, in com- 

 mon with some other animals under simi- 

 lar circumstances, almost white. As the 

 tide recedes, they recede along with it ; 

 and if accidentally left behind, take shel- 

 ter beneath stones on the shore. 



