FLATWORMS 



Fig. 1 1 .8. Regeneration in pianarians. The regeneration of pieces, cut from a worm along the 

 lines marked in .-1, is shown by the labeling of the remaining figures. For example, a piece re- 

 moved bv cuts along lines de and fg regenerates as shown by the figures marked defa. Stippled 

 areas represent portions formed as new tissue during the early stages of regeneration. 



indicated, the muscles, the enteron, and the reproductive systems are sur- 

 rounded by mesenchyme which fills the space within the body wall. The 

 mesenchyme contains epidermal gland cells responsible for the secretion of 

 mucus and of the bodies called rhabdites whose function is problematic; 

 the gland cells open on the surface of the body. In the meshes of the 

 mesenchyme are also found the formative cells whose role in regeneration has 

 just been described. The relation between the mesenchyme and the excretory 

 system has also been pointed out earlier. 



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