The Philippine Journal of Science 

 Table 1. — Showing variation in size of eggs of Oxyuris equi. 



% Egg No. 



Length. 



Width. 



Egg No. 



Length. 



Width. 





E 



1 





85 



i 































89 























Eggs considerably smaller than those recorded in Table 1 

 are occasionally found, but they are rare and probably abnormal 

 since no miniature embryonated eggs have been observed in 

 any of my cultures. 



OVIPOSITION 



Oviposition has been repeatedly observed in vitro, and in 

 many cases certain specimens that were kept overnight in the 

 laboratory in beakers containing physiological salt solution 

 yielded many eggs that were found floating on the surface of 

 the liquid, the eggs being agglutinated by a gluey substance 

 that is insoluble in water and in physiological salt solution 

 (%. 1). 



So far as my observations go, long-tailed forms of Oxyuris 

 equi (mastigoides type) almost invariably oviposit in vitro, 

 discharging practically the entire egg content, whereas short- 

 tailed forms (curvula type) seldom oviposit under similar con- 

 ditions; but few eggs are discharged from these ovipositing 

 forms, the bulk of the eggs being retained in the uteri In 

 this connection it may be mentioned that long-tailed forms of 

 Qxyuns equi are comparatively scarce in native horses and that 

 they are usually located in the caacum, whereas short-tailed 

 forms are usually located in the colon, in which organ thev were 

 frequently found in large numbers (fig. 2). 



Oviposition in Oxyuris equi is preceded by prolonged contrac- 

 tions of the uterus whose movements may be characterized as 

 peristaltic. Uterine contractions are practically the onlv evi- 

 dence of vitality of horse oxyurids, since I have never observed 

 the characteristic nematoid movements in these parasites and 



