351] NORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 71 



Lymph System. — The lymph system is similar to that described for 

 A. magnum and consists of the three longitudinal canals on either side 

 of the body, one canal lateral to each cecum and a pair, one dorsal and 

 the other ventral, mesal to the diverticulum of either side. The secon- 

 dary branchings could not be traced but lymph sinuses are present in sec- 

 tions in all parts of the body, and those around the acetabulum are shown 

 in Figure 68. 



Excretory System. — The excretory pore is median, dorsal, at the 

 level of the cephalic margin of the acetabulum. A short median vesicle 

 passes ventrad and anteriad and divides into two collecting vesicles as in 

 A. magnum. These pass ventrad and posteriad, one on either side, loop 

 around the caudal ends of the diverticula, and then turn anteriad, wind- 

 ing around the ceca in many irregular coils so that in sections they ap- 

 pear lateral, mesal, ventral or dorsal to the intestine; often the tube is 

 cut two or three times in the same section or a single section may show 

 a coil encircling the cecum for half or more of its circumference (Fig. 

 67). Anterior to the bifurcation of the alimentary tract the ducts con- 

 tinue in the lateral areas of the body and can be traced almost to the oral 

 sucker. 



THE GENUS ZYGOCOTYLE 



The only known form with which the paramphistomes from the duck 

 can be compared is Amphistoma lunatum. This species was described 

 by Diesing (1836) ; the material had been collected by Natterer in Brazil, 

 South America, from the cecum of Anas melanotus, A. ipecutiri, A. 

 'tnoschata, Himantopus wUsonii, and also from the cecum of Cervus 

 dichotomus. Fishoeder secured the original specimens from the Vienna 

 museum and (1903) gave a more extended description of the form, altho 

 his study was restricted to the examination of toto preparations. He 

 stated that the citation of Cervus dichotomus as a host of this form is 

 probably an error, and the same suspicion had been mentioned by Diesing 

 (1850). It is at once apparent that the present species is very similar 

 to A. lunatum. Both are parasites of American ducks, and are the only 

 paramphistomes at present known from avian hosts. They are nearly 

 equal in size, are similar in shape, have a subterminal oral sucker, re- 

 productive systems that compare very closely, digestive tracts similar 

 in character, and acetabula of the same form consisting of an anterior 

 section and a posterior overhanging lip which terminates on either side 

 in a small cone-like projection. 



Amphistoma lunatum has been placed as an appendix to every classi- 

 fication of the paramphistomes that has ever been attempted. With the 

 discovery of a form so similar, the two must belong together and a 

 new genus is proposed to contain the two species. The peculiar divided 



