252 L. B. SEELY. 



The uterus is a continuation of the oviduct, running to the 

 posterior end of the anima-1, then forward to the genital pore. It 

 winds about, filling the spaces between the other organs, and in 

 the case of adult worms often nearly covers them. It is circular 

 in cross-section, and about .15 mm. in diameter. In the adult 

 animal this tube is filled with eggs which as they ripen take on 

 a dark brown color, and give the worm a peculiar mottled ap- 

 pearance. There are no lateral longitudinal folds as in the case 

 of most of the other species of this genus. 



P. coinplexus is closely related to P. siini/iplcxus, described by 

 Stafford (1902) under the name of H&matolcechus similiplexus. 

 The principal differences between the two species are that in P. 

 coinplexus the testes are very much larger than in P. similiplexus ; 

 there are no lateral longitudinal folds of the uterus ; and the eggs 

 are considerably smaller, being .029 mm. by .014 mm. as com- 

 pared with .039 mm. by .019 mm. in P. similiplexus. In outer 

 characters, --size, shape, suckers, etc., there is a close simi- 

 larity between the two species. P. similiplexus is covered with 

 spines, while P. coinplexus is probably smooth. In this respect 

 P. coinplexus resembles P. longiplcxus. In respect to the folds 

 of the uterus it most closely resembles P. medioplexus. The 

 ascending and descending coils seem however to have less regu- 

 larity that in that species. 



The other species of this genus are universally reported as 

 being found in the lungs of frogs, while, as has already been 

 noted, these specimens were labelled as having been found in the 

 mouth of the leopard frog. Upon inquiry I found that these 

 distomes are rarely or never found in the mouth of a living or 

 freshly-killed animal. If, however, the frogs are killed by 

 chloroform, and especially if they are left for some time in the 

 killing jar, the worms, still alive, may frequently be found in the 

 mouths of the dead animals. They may be thrown from the 

 lungs by the struggles of the dying animal, or they may find 

 their way to the mouth in their efforts to escape from a dead 

 host. At any rate the above facts explain their being found in 

 the mouth of the frog, and leave every probability that P. com- 

 plexus is a lung parasite. 



