384 



ARTICULATA : WORMS. 



The sexes are combined in each proglottis or joint. From 

 time to time the hindmost joints become detached, and 

 in this way the length of the tape-worm is limited, not- 

 withstanding the constant growth of joints from the head 

 and neck. 



Tape-worms have no mouth nor alimentary canal. Their 

 nourishment is absorbed through the walls of the body. 



SUB-SECTION IX. 

 THE ORDER OF TURBELLARIA. 



THE Turbellarians differ from all the other groups 

 placed under the Sub-class of Helmintha in the fact 

 that they are not parasites. 



FIG. 519.* 



Planarian Worm, Planoceranebulosa, 



Most of the Turbellarians inhabit fresh water; some 

 kinds are found in the sea; and a few on the land. 

 They are elongated and flat worms, and are covered with 

 cilia, and are destitute of suckers. Planaria and Nemer- 

 tes are examples. 



* Figs. 510, 512, 514, 516, 519, 520, 54, and 655, are from the works of 

 Professor A. E. Verrill. 



