THE DENDKOCCELA. 



161 



known as Planarice belong to this division. Some are ma- 

 rine, some fresh-water, and some terrestrial. 



In the fresh-water forms, the female reproductive appa- 

 ratus has a distinct vitellarium, as in the higher Hhahdocoela, 

 and there is only one common genital aperture. But, in the 

 marine Planar ioe (Fig. 33), there is no vitellarium ; the ova- 

 ries and testes are numerous, and scattered through the meso- 

 derm, being connected with the exterior by ramifications of 

 the oviducts and of the vasa deferentia. A ramified gland, 

 which secretes a viscid albumen or envelope for the eggs, 



Fig. Zi.—Polycdis (Leptoplana) IcBvigata (after Quatrcfast^p)-— o, mouth; ft, buccal 

 cavity; c, (Esophageal orifice ; d, stomach ; e, ramifications of gastric caeca; f, 

 ganglia ; g, testes ; h, vesiculiB seminales ; i, male genital canal and peuis ; k, ovi- 

 dacts ; /, spermathecal dilatation at their junction ; m, vulva. 



opens into the vagina, and the female is distinct from the 

 male aperture. Planaria dioica is unisexual. 



In some of the Planarice there are distinct water-vascular 



