46 The Philippine Journal of Science 1923 



on the other hand, found larvae in the lungs of a guinea pig 

 that had been fed infective larvse of the stomach worm of sheep 

 and cattle, Haemonchus contortus. 



Fiillerborn,(2) who carried out some preliminary experiments 

 with the pinworm of man, Enterobius (Oxyuris) vermicular is, 

 expresses the view that a migration of the larvse of this parasite 

 to the liver and lungs appears improbable, in view of the phylo- 

 genetic position of the Oxyuridae. 



The failure to find larval migrations in the Heterakidae (He- 

 terakis and Ascaridia), a group that is zoologically more closely 

 related to the Ascaridae than are the Oxyuridae, does not warrant 

 the expectation, from the phylogenetic viewpoint, that the larvse 

 of oxyurids undergo migrations comparable to those of ascarids. 



DEVELOPMENT OF OXYURIS EQUI IN THE HORSE 



Railliet and Henry (5) described larval forms of Oxyuris equi 

 from the horse measuring from 5 to 10.5 millimeters, in which 

 the anus was situated relatively far from the posterior extrem- 

 ity; they also described larvae of less-common occurrence, from 

 5 to 6 millimeters in length, in which the distance of the anus 

 from the posterior extremity was shorter than in the former 

 types. Railliet and Henry expressed the opinion that these forms 

 represented males and females, respectively, and they predicted 

 that following one more molt (the final larval molt) , sex differ- 

 entiation would become apparent. Recently Ihle and Van 

 Oordt(4) found larvae of Oxijuris equi in a similar stage of devel- 

 opment, the smallest form measuring a little less than 3 milli- 

 meters. These writers also found molting forms and their 

 observations on these larvae established the correctness of the 

 opinions expressed by Railliet and Henry regarding sexual 

 differentiation of the larvae subsequent to the final larval molt. 



SUMMARY AND CONCLUSIONS 



The data presented in the foregoing pages can be briefly 

 summarized as follows: 



1. Long-tailed horse oxyurids (mastigoides type) commonly 

 oviposit in vitro, the eggs being segmented when they are dis- 

 charged from the uterus. Uterine eggs that are liberated by 

 cutting up female worms are nonsegmented and do not develop 

 in vitro. Short-tailed oxyurids (curvula type) rarely oviposit 

 in vitro. Eggs that are normally discharged from these forms 

 develop normally in vitro. 



