ART. 17 PARASITES OF AMPHIBIA AND EEPTILIA HARWOOD 51 



In the paper referred to (Harwood, 1930) I have recorded this 

 species from a considerable number of amphibians and reptiles, and 

 several others have been added since. The complete host list is now 

 as follows : Triturus viridescens, T. ineridionalis^ Aiiiby stoma fni- 

 crost077ivm, A. talpoideum, Hyla squirella^ Pseudacris triserlata, 

 Rana areolata^ R. 'palustris, R. sphenocephala^ R. sylvatlca, R. cJami- 

 fans, R. catcshelana, Bufo valliceps^ B. ferrestris^ Gastrophryne are- 

 olata, Ophisauims ventralis, Lelolopisma laterale^ Eumeces fasciatus, 

 Heterodon coutortrix^ Storeria dekayl^ Micrwus fulvius^ Terrapene 

 earolina trlunguis^ and Terrapene ornata. It may be noted that the 

 majority of these hosts are mainly terrestrial. R. catesheiana is the 

 most nearly aquatic host, but only a very light infection was encoun- 

 tered in 20 specimens of this frog examined. In the laboratory cul- 

 tures the larvae do not develop in saturated soil. 



An interesting variation of this species has been obtained from 

 Eumeces fascmtus. The worms from this host are unusually small, 

 the males being only 1.65 to 2.2 mm long. The spicules are variable, 

 often being unequal. In one worm the long spicule was 0.233 mm 

 long and the other only 0.1G6 mm long. The large papillae are often 

 without the cuticular tubercles around them. All these characters 

 appear, though seldom in such a pronounced manner, in immature 

 worms from Bufo valUceps, a common host. The worms from E. 

 fasciatus^ however, are mature, as is shown by the presence of fertile 

 eggs in the females. The females from this host are also ver}^ small. 



Travassos (1931) gained the impression that I (Harwood, 1930) 

 included a number of species in my discussion of C osmocercoid es 

 dukae. It may be well to emphasize, therefore, that the recorded 

 variations other than size can not be correlated in any way with the 

 type of host invaded. Indeed, on studying material obtained by fur- 

 ther collecting, those few groups mentioned by me (1930) have 

 been found to be untenable. That free-living animals possessing a 

 wide geographic range, and living under a variety of conditions, 

 show a great range of variation is a well-known biological principle. 

 Two examples come readily to mind; namely, MeJospiza nielodia 

 among the birds, and Papilio glaucns among the insects. Accord- 

 ingly, we might expect to find a great range of variation among those 

 parasites that are able to invade a variety of host species. This has 

 been amply demonstrated with Syngmnus trachea. 



Family ATRACTIDAE Travassos, 1920 (?) 



Genus ATRACTIS Dujardin, 1845 



This is a genus of very small worms that are parasitic in reptiles. 

 Only one species, A. opeatura Leidy, has previously been described 



