422 



SYNGONY IN OXYURIDS 



Diagnosis. Thelastoma (Thelastomellum) myolabiatum n. sp. Dimen- 

 sioned as shown in the formula, and with lips and amphids as in Fig. 5. 



3. SYNGONY IN A NEW NEMA FOUND IN MILLIPEDS 



Hitherto undescribed nemic parasites found in the intestine of the milliped 

 Fontaria marginata Say and belonging to the genus Thelastoma Leidy, 

 prove syngonic. Thelastoma would be assigned by 

 most authors to the group Oxyuridae. 



The discovery of syngony in this group opens up an 

 interesting field for speculation and research. It has 

 long been felt that the "Oxyuridae" present many 

 resemblances to the rhabdites. The gonism of the 

 rhabdites has been found very varied, particularly 

 through the researches of Maupas. Query: To what 

 extent, now, will the variations exhibited by the 

 rhabdites be found to occur in the "Oxyuridae?'' 



Male "oxyurids" usually are less common than the 

 corresponding females, quite frequently are rare, and 

 in some cases are unknown. The striking nature of 

 the recorded sex ratios has been explained by saying 

 that the males, being very much smaller, are easily 

 overlooked, and that possibly they die soon after 

 copulation; and that these two factors, their small- 

 ness and (assumed) relatively early death, account 

 for their supposed rarity. 



In the rhabdites the evidence fully warrants the 

 matic'drawf^of'tiTfe^ vi ew that syngony has evolved from amphigony with 

 male gonads of ^Thelastoma a gradual diminution or disappearance of males; 

 " for many stages between the two extremes still exist 

 as evidence of the possibility of such a change. There- 

 fore the discovery of syngony in the "oxyurids" at 

 once suggests a new explanation of the scarcity of 

 "oxyurid" males, namely, the one now usually accepted 

 in many cases for the rarity of male rhabdites. If 

 this be true of the "oxyurids," it may have a con- 

 gonicspermsof sHWoSomd- siderable bearing on veterinary and medical questions 

 lwm ' connected with "oxyurid" parasites in man and 



domesticated animals, and in other hosts. 



Species that have been assigned to the "Oxyuridae" are common parasites 

 of insects and some other annulata. 



inl 



ordct 



iX40 an. 



(right), sp. the. sperma- 

 theca. 



