40 The Philippine Journal of Science 1923 



up finely with a pair of scissors, thus liberating the eggs, which 

 may be planted on a charcoal and faeces mixture, in water, or 

 in any other suitable medium. This procedure was found to 

 be inapplicable to Oxyuris equi, because numerous attempts to 

 bring about the development of the eggs of this parasite by 

 planting artificially liberated eggs in water, in physiological 

 salt solution, on charcoal and fseces mixtures, in 2 per cent as 

 well as in weaker dilutions of formalin, were invariably un- 

 successful. The eggs underwent degenerative changes in all 

 media except formalin solution, in which liquid they remained 

 intact for some time. 



Artificially liberated eggs of Oxyuris equi, secured as a result 

 of chopping up the worms, differ from normally discharged 

 eggs in that the egg substance has a finely granular appearance, 

 fills almost completely the interior of the shell, and shows no 

 trace of segmentation. In the opercular end of these eggs one 

 or two spherical areas less dense than the remaining egg sub- 

 stance are present (Plate 1, fig. 1) . In eggs that are discharged 

 from the uterus the egg substance appears as a compact coarsely 

 granular mass, more or less spherical in shape, and filling only 

 the central portion of the interior of the shell, leaving empty 

 spaces at both poles. Moreover, the egg substance shows decided 

 segmentation (Plate 1, fig. 2) . 



In a number of cases I examined eggs shortly after they were 

 oviposited following the application of artificial stimuli and 

 found them to be segmented, thus showing that segmentation 

 occurs rapidly, probably while the eggs are still in the uterus. 



The failure of eggs, artificially liberated by chopping up 

 female oxyurids, to develop and the rapidity with which ovi- 

 posited eggs develop in vitro indicate that some profound change 

 occurs in the eggs shortly before they are laid. Whether this 

 change is that of fertilization, or whether it is due to the early 

 cleavage stages that probably occur before oviposition, has not 

 been determined. 



Another respect in which artificially liberated eggs differ 

 from those that are normally expelled by the female parasites is 

 that the former sink to the bottom of liquid containers in one 

 solid mass that can be broken up only with considerable dif- 

 ficulty, owing to their being firmly agglutinated. When broken 

 up into small thin masses the latter may come to the surface. 

 Normally discharged eggs float almost invariably on the sur- 

 face of water and salt solution. Some eggs that are liberated 

 from short-tailed females, as a result of the application of arti- 



