14 SYNOPTIC KEY 



5(6) Alimentary canal with three primary branches, one 

 extending forward, two backward; each primary 

 branch bearing secondary branches (diverticula); 

 marine, fresh water and terrestrial. (Pratt, 164; 

 W. and W., 354.) Order Triclada 



6(5) Alimentary canal with many primary branches which 

 possess diverticula; marine. (Pratt, 169.) 



Order Polyclada 



Class TREMATODA 



1(2,^3) Posterior organs of attachment powerfully developed. 

 Suckers at least three in number; hooks and anchors 

 usually present; usually ectoparasitic. (Pratt, 173; 

 W. and W., 374.) Order Monogenea 



2(1, 3) No hooks in suckers or sucking disks; posterior end 

 without suckers or with weakly developed suckers. 

 Either a large ventral sucking disk or a midventral 

 row of suckers. No oral sucker. Mostly endo- 

 parasitic. (Pratt, 178.) Order Aspidocotylea 



3(1, 2) Suckers two in number; one ventral, the other anterior 

 about the mouth; endoparasitic; no hooks in suckers 

 or sucking disks. (Pratt, 179; W. and W., 379.) 



Order Digenea 



Class C E S T O D A 



1(2) Body not divided into proglottids (segments). (Pratt, 

 192; W. and W., 429.) Subclass Cestodaria 



2(1) Body consisting of head or scolex and a chain of pro- 

 glottids. (Pratt, 192; W. and W., 430.) 



Subclass Cestoda 



Phylum NEMATHELMINTHES 



1(2) A longitudinal lateral line present on each side of the 

 body. Mouth and alimentary canal present. Endo- 

 parasitic or small worms in water, soil, or plants. 

 fPratt, 214; W. and W., 482; F. S. and T., 374.) 



Class and order Nematoda 



