345] XORTH AMERICAN PARAMPHISTOMIDAE—STUNKARD 65 



Mention has previously been made of the anatomical differences existing 

 between these species and a statement ventured that such wide and fun- 

 damental differences should not be present in a natural genus. A. mag- 

 num agrees with S. scleroporum in general appearance and size, in type 

 of excretory and lymph systems, character of vitellaria, and in 

 general type of reproductive and alimentary organs; but A. mag- 

 num has large oral evaginations, which pockets are reduced and do not 

 extend outside the sucker in S. scleroporum, and A. magnum lacks the 

 preoral sphincter which is present in 8. scleroporum. In A. magnum 

 the uterus and cirrus sac open to the surface thru a common hermaphro- 

 ditic duct; in S. scleroporum they open separately. Looss (1899 : 551) 

 says one of the most important of generic characters is the structure of 

 the copulatory organs. In A. magnum the testes are further posteriad 

 and the ovary is situated one-fourth to one-third of the body length from 

 the posterior end instead of at the level of the anterior margin of the 

 acetabulum as is the case in S. scleroporum. In S. scleroporum the testes 

 and ovary are widely separated and in A. magnum they are compara- 

 tively close together. These differences appear to be of sufficient impor- 

 tance to exclude the American species from the genus Schizamphistoma. 



A. magnum agrees with 8. spinulosum in the presence of oral evag- 

 inations and lack of preoral sphincter, but differs from it in the manner 

 of the coiling of the excretory vesicles, in the presence of a common herm- 

 aphroditic duct and in the character of the vitellaria, as well as the rela- 

 tive positions of the testes and ovary. The morphological facts show 

 differences too fundamental to permit the inclusion of both these species 

 in a single genus. 



Alassostoma parvum agrees with A. magnum in general morpho- 

 logical features, presence of oral evaginations,, lack of preoral 

 sphincter, type of lymph and secretory systems, character of geni- 

 tal organs and ducts, also in relative position of testes and ovary. A. 

 parvum therefore agrees with and differs from 8. scleroporum and S. 

 spinulosum in the same manner as A. magnum. That the two forms are 

 not different developmental stages of the same species is shown by the 

 great difference in the size of the worms and the relative differences in 

 the size of suckers and genital organs. One of the species of A. magnum 

 10 mm. long is not sexually mature, while in the sectioned specimen of A. 

 parvum which is less that 3 mm. long spermatoza were present in the tes- 

 tes and vas deferens. Further, ova were present in the oviduct, and the 

 ootype and anterior part of the uterus were filled with spermatoza. 

 Eggs were present in only one of the seven specimens of A. magnum and 

 the absence of eggs in the three specimens of A. parvum does not signify 

 that it is a young stage of A. magnum. A. magnum is large and has 



