23,i Schwartz: Life History of the Horse Oxyurid 39 



siological salt solution. The following artificial stimuli were 

 used to bring about oviposition in vitro. The water or salt- 

 solution medium was acidulated and rendered slightly alkaline; 

 the medium was gradually heated by addition of hot liquids 

 (hot water and hot physiological salt solution being added to the 

 respective media) ; the worms were transferred from water to 

 salt solution and vice versa; the worms were transferred sud- 

 denly from a cold medium to a warm medium. The results 

 obtained in these attempts were as follows : 



Specimens that exhibited no uterine movements could not be 

 stimulated to uterine contractions by any method; these forms 

 were probably nonviable. Females that exhibited uterine con- 

 tractions generally reacted positively to artificial stimuli. As 

 a result of transferring the worms from water to salt solution 

 and vice versa, the uterine contractions were generally accele- 

 rated. Gradually heating the medium in which the worms were 

 contained and the sudden transfer of the worms from a cold 

 to a warm medium had a very marked influence on the move- 

 ments of the uterus which became intensified; these intense 

 contractions continued after the liquid had cooled and resulted 

 in an explosive discharge of eggs with eversion of the uterus 

 through the vaginal opening. 



Several years ago I made similar observations on oviposition 

 in a species of Oxyuris from a chimpanzee from the National 

 Zoological Park at Washington, D. C. Numerous specimens, 

 all females, were obtained from the monkey following the 

 administration of an enema. The parasites were alive and 

 when viewed through a binocular microscope marked movements 

 of the uteri were observed, these movements terminating with 

 the discharge of stringy masses of eggs. In a second lot of 

 worms obtained from the same monkey, the parasites were 

 transferred to warm physiological salt solution, which resulted 

 in rapid liberation of the eggs. Following the expulsion of the 

 eggs the worms became quiescent. 



Seurat(8) records similar observations on egg laying in a 

 species of oxyurid in which oviposition was preceded by uterine 

 contractions which resulted in the liberation of the eggs in long 

 strings. 



DEVELOPMENT OF EGGS 



The usual procedure that is followed in order to obtain large 

 numbers of eggs of a given species of nematode for life-history 

 studies consists in securing mature females and chopping them 



