172 OXYURIS-LARV^E HATCHED IN THE HUMAN STOMACH, 



largest of the hatched larvae did not much exceed 0-11 mm., while 

 the smallest had hardly developed beyond the tadpole stage at 

 which they were inserted. Thus it will be seen that it is not 

 necessary that the eggs of Oxyuris vermicular is should 

 undergo any considerable development outside the body of its host, 

 though normally they do so without a doubt. What would have 

 been the fate of these smallest larvje no one can tell. I believe 

 they would if left free in the alimentary canal have lived and 

 developed. The cuticula was already well-formed, and, with the 

 very highest powers, visibly transversely striated. 



A comparison of the unliatched specimens with the empty shells 

 proved that the embryos escape from the egg in a uniform and 

 definite way. I already knew of the existence of pores in the shell 

 of the eggs of this species of Oxyuris. I discovered them 

 while attempting to I'ear the larvte from eggs kept in artificial 

 digestive fluids,* in which attempt I failed. I found, however, 

 that after about twenty-four hours at body temperature the arti- 

 ficial digestive fluids brought to view distinct pores in various 

 parts of the shell. The distribution of these pores seemed* 

 to me at the time quite irregular, and I never saw more than two or 

 three in close proximity. I overlooked entirely a phenomenon 

 which was first brought to my notice by experiment two here 

 described, namely, the existence of a distinct area (PI. viii, Fig. 1), 

 where these pores are very numerous and tohich becomes the place of 

 exit of the embryo. I was first made aware of this fact on com- 

 paring with each other the empty shells fiom which embryos had 

 made a normal exit. These empty shells were without exception 

 ruptured at the same place. To locate this place accurately it 

 will be necessary to describe the egg. The eggs of most species 

 of Oxyuris are more or less irregularly spindle-shaped. The 

 irregularity consists in a curvature of thelongaxis in thedorso-ventral 

 plane of the future embryo. Furthermore, the two rounded ends 

 of the egg are dissimilar, the anterior end, speaking again from 

 the position of the futui'e embryo, being more pointed than the 

 posterior. When therefore the egg is viewed in profile, and this 



* Lactopeptine and other propi'letary preparations. 



