468 



anterior part of the "neck" of the vagina (figs. 180, 184). 

 Meanwhile the cells of the lower layer have been difiEerenti- 

 ating. They elongate considerably, and develop, after about 

 two days, a very long narrow lumen, one end of which becomes 

 applied by a funnel-shaped process to a gland cell, while the 

 other opens into the upper part of the ovipositor. Practically 

 the whole of the cell cytoplasm becomes converted into this 

 duct, the nucleus itself remaining as a small heavily staining 

 swelling upon it. 



The function of these glands is apparently to secrete a 

 lubricating liquid into the chitinous ovipositor, and aid in the 

 passage of eggs down this structure, while assisting it, at the 

 same time, to bore through the hard shell of the fly pupa 

 during oviposition. This liquid is clearly seen during the 

 act of laying as minute oily globules which ooze through the 

 sheaths of the ovipositor. 



On the upper surface of the vagina two small rounded 

 vesicles are seen (figs. 180, vsc), whose walls are composed of 

 long columnar cells. They appear to correspond to structures 

 which in the honey bee are described as aiding in copulation, 

 a kind of bursa copulatrix; what their actual function in 

 Nasonia is, I am unable to say; that tbey have nothing to 

 do with copulation seems fairly certain, since this takes place 

 by the application of the penis of the male to the termination 

 of the ovipositor of the female. 



The first stages in the development of the great accessory 

 glands from the posterior part of the vagina have already been 

 described. Two curious changes now take place in connection 

 with the openings of these glands, which tend to confuse their 

 true origin : firstly, the vagina grows backwards over the 

 openings of the glands, so that they now arise not pos- 

 teriorly from the vagina, but from its antero-ventral region ; 

 secondly, shortly after the glands grow out from the vagina 

 they draw a portion of the cavity of this structure after them, 

 so that they open in the twenty-four hour pupa, not directly 

 into the vagina, but into a separate chamber, lying beneath 

 it, and opening into the "neck" of the vagina, shortly before 

 its opening into the ovipositor. 



The cells on the upper part of this sac elongate con- 

 siderably to form a columnar epithelium ; in the late stages 

 of pupal life (four and a half-day pupa) their very powerful 

 staining capacity shows that they have now developed into 

 gland cells. 



Tlie two posterior accessory glands increase in length, and 

 in the pupa one day old have approximately attained to their 

 adult dimensions. The glands are not symmetrically placed ; 

 that on the right side is much the longer of the two (fig. 180), 



