GENERATIVE ORGANS OF NEMATOIDA. 297 



ments of the egg in the uterus. I have also seen a peculiar 

 condition in those eggs of Oxyuris vermicularis, which pass last 

 out of the uterus in artificially produced oviposition (which never 

 succeeded with me except when the Oxyurides were put quickly 

 upon an object-glass, covered with a small glass, without turning 

 them at all upon their axes, and only then covered with saliva). 

 At one end, probably the hinder one, they bear a light hood or 

 cap, which, as it afterwards disappears, is probably nothing but 

 the expression of the fact, that in them the deposition of the 

 chorion is not yet complete. In the uterus, during the deposi- 

 tion of the eggs, we see the most beautiful peristaltic move- 

 ments, of alternate undulatory constriction and dilatation. 



6. The Vagina. It is covered with an epithelium of the form of 

 that of the uterus, which, however, is usually smaller, and appears 

 sometimes more or less, and sometimes not at all, swollen and 

 thickened at its external orifice. At its outer extremity it is 

 dilated into a campanulate form, and has a transverse cleft in 

 the middle. It appears to be closed by a pair of lobes or valves, 

 which rest together in the middle. When a number of eggs has 

 collected in this bell, they force the lobes asunder, the cleft 

 opens, and the eggs are laid by jerks, in Oxyuris always several 

 together. 



The principal question now is : Where are the eggs fecun- 

 dated, and what subsequently takes place in them? With 

 regard to this process we are still very much in the dark ; and 

 the following four views come into opposition with each other. 



1. NELSON first asserted that the peculiar seminal corpuscles 

 press themselves into any part of the surface of the vitellus, or 

 become pressed into it by the contraction of the oviduct, but 

 that they do not penetrate of themselves into the vitellus, and 

 that the chorion is only formed subsequently around this vitelline 

 mass. According to Meissner, fecundated eggs are always cha- 

 racterised by an irregular, as it were ruptured, surface, and this 

 appearance is not to be regarded as accidental, or produced by 

 mechanical action. 



2. BISCHOFF denies that there is any penetration of the 

 seminal corpuscles, and thinks that the structures described as 

 seminal corpuscles were epithelium, which had accidentally 

 attached themselves to the vitellus, or had penetrated into it. 

 W^edl also represents them as epithelium. Nelson has recently 

 stated that he is very well acquainted with the large nucleated 



