112 The Philippine Journal of Science 1915 



in the same dish with a female, but this did not seem to influence 

 the number or condition of the eggs laid. 



Typical eggs of Ascaris lumbricoides are more or less oval 

 in form. They average about 70 micra in length and 50 micra 

 in thickness, although the variation in size and curvature is 

 rather great. The egg consists of a central mass of protoplasm 

 and yolk with a very thin vitelline membrane, surrounded by a 

 thick transparent shell consisting of an inner layer of chitin and 

 an outer layer of some albuminous material. The chitinous 

 inner shell is made up of two parts, a thin, tough, very refrac- 

 tive layer, and a thicker, more brittle, outer layer which often 

 shows very delicate striations. The egg does not entirely fill 

 the shell, but forms a round ball in the center with a clear space 

 at each end. The polar bodies often may be seen in one of these 

 clear spaces in a newly laid egg. 



On the outside of the chitinous shell is a thick layer of album- 

 inous material, which is raised all over the surface into small, 

 round, blunt protuberances, producing a very characteristic 

 mammillated appearance. This layer is colorless in eggs laid in 

 the laboratory, but in the faeces it generally is colored by the bile 

 pigment. It adheres very tightly to the chitinous part of the 

 shell, and I have never been able to remove it without destroying 

 the egg. When the eggs are first laid, this outer layer is some- 

 times very soft and sticky, and this fact accounts for one of the 

 commonest atypical forms which is found in the faeces. This 

 is the form in which the mammillations are missing and the 

 albuminous layer is denser than in the typical mammillated 

 form. This condition may be produced by shaking together 

 freshly laid mammillated eggs or by rolling them about between 

 two smooth surfaces while they are still soft. The mammilla- 

 tions are smoothed down, and the layer becomes more compact. 

 It seems very reasonable to suppose that the same thing may 

 occur sometimes in the intestine, particularly if the eggs be laid 

 a little prematurely. 



Another atypical form which is often found in faeces differs 

 from the typical eggs in that the outer albuminous layer of the 

 shell is entirely absent, and the surface, which is formed by the 

 outer chitinous layer, is perfectly smooth. Eggs of this kind are 

 the most difficult to diagnose, as they are easily mistaken for 

 the eggs of other forms of worms, and there even has been 

 some doubt as to whether they were the eggs of A. lumbricoides 

 or of some closely related species. It is suggested by some 

 authors that these eggs are produced by the shelling off of the 



