THE PROCTUCHA. 



165 



cles are developed on the head in front of the prae-oral ciliated 

 band. But, as development advances, the segmentation be- 

 comes obliterated, the ciliated bands and the feelers vanish, 

 and the worm assumes the characters of a Xemertean.' 



Fig. 3 



Fig. 36. 



Fig. ST>-^7.— PiHdium gyrans (after Leiickart and Pao^enstechei). 



.35. Young Pitidiuni : a, alimentary canal ; b, rudiment of the Nemerteau. 



3(i. PUkliwn with a more advanced Nemerteau. 



37. Newly-freed Nemertean. 



In species of the genus Linens^ the ciliated embrvo which 

 leaves the egg is speedily converted into a body like a helmet 

 with ear-lappets, and having a tuft of cilia in place of a plume 



1 It is very probable, however, tbat this larva belonsrs to the orenus Polygor- 

 dius, which appears to be an annectent form between tlie Turbellnrln and other 

 groups. See Schneider, " Ueber Ban und Entwickelung von Polygordius." 

 (" Archiv fur Anatomic und Physiologie," 1868.) 



