70 PLATYHELMINTHES 



The female organs are as follows: 



(a) Opening into the genital atrium are the two large 

 sacs, the so-called uteri, which lie near the margins, just pos- 

 terior to the end of the pharynx. Each has a separate open- 

 ing on the ventral surface of the body, but has no direct 

 connection with any other part of the reproductive system. 

 These may not be homologous with the single uterus found 

 in most triclads. (See Wheeler.) 



{b) Place a worm ventral side up and look carefully be- 

 tween the second and third or the third and fourth anterior 

 gut diverticula on either side of the main anterior ramus for 

 the two ovaries. 



(c) The oviducts pass backward from the ovaries, parallel 

 to the vasa deferentia, and unite posterior to the penis. The 

 common duct thus formed enters the posterior part of the 

 genital atrium. The oviduct is difficult to demonstrate and 

 it may be necessary to try both fresh and stained material. 



{d) Along the margins of the animal, between the, diver- 

 ticula of the gut, are rounded bodies, the vitellaria. These 

 discharge their products into the oviducts. What is their 

 function? 



Draw the female reproductive system. 



Study stained and mounted specimens for any points 

 which have not been found, and particularly examine the 

 nervous system. Look for the marginal nerve running along 

 the edge of the body, and for numerous transverse commis- 

 sural nerves. How many of these are there? How regular 

 is their arrangement? 1 



Wheeler: Syncoelidium pellucidum, a new Marine Triclad. Jour. 

 Morph,. 9, 1894. 



TREMATODA 



Trematodes are flat worms which lead a wholly parasitic 

 life, but which have retained, to a greater or less degree, those 



X A Polyclad, Planocera, can often be obtained from the mantle 

 chamber of Busycon. If Busycon is allowed to remain out of water for 

 some hours the Planocera usually crawl out. The form is fairly satis- 

 factory for study. 



