INTERNAL ANATOMY. 103 



not able to suggest ; it is probably due to his imper- 

 fect methods of examination ; in the absence of dissec- 

 tion and section-cutting, and to the great transparency 

 of the oviduct when distended by eggs. Whatever be 

 the explanation, I can only agree with Nalepa that 

 Haller's account is purely imaginary. 



The Vagina, PL B, fig. 8, va. 



The two oviducts join, as before mentioned, at their 

 anterior ends, almost immediately above the vulva : 

 they coalesce, forming one broad short tube which 

 turns downward from the oviduct ; it is perpendicular 

 in the body, and at right angles to the genital ring, 

 which nevertheless it completes. It is more than the 

 diameter of the two oviducts together. It has thick, 

 muscular walls in its proximal part, and is the organ by 

 which the egg is extruded from the body ; the lower, 

 distal portion in such species as Glyeyphagus platy- 

 (jtister however is far thinner and more flexible ; and 

 has a large transverse fold which, when it contains an 

 egg, expands and forms almost a chamber; but when 

 empty collapses, forming the fold (PL B, fig. 10, ode), 

 which greatly resembles the distensible chamber in the 

 ductus ejaculatorius of the male (PL B, fig. 6, dec). 



The Vulva, 



This is the aperture by which the egg escapes from 

 the body ; it must be remembered that it is an egg- 

 laying aperture only, not one through which the female 

 is fertilised. When seen from the exterior, i. e. from 

 the ventral surface of the body, it most frequently pre- 

 sents at first sight somewhat the appearance of an 

 inverted letter Y, but it must be one where the two 

 arms are somewhat curved (PL VII, fig. 2, etc.) ; this 

 Y generally seems to be formed of dark-coloured chitin. 

 The appearance is due to the fact that the external 

 opening of the vagina is closed, except at the moment 

 of oviposition, by two lateral labia, which are pressed 



