MORPHOLOGY OF THE LEPIDOPTERA. 165 



PL XIX., which in the case of my specimens indicates a lapse of about three days or 

 rather more from the close of the previous stage. The communication is figured 

 PI. XIX. tig. 62. I am inclined to think that it is not established sometimes till a yet 

 later period. 



There is nothing much to be noted in the histology of the organs during this stage. 

 Their walls are composed of a single layer of cells. The chitinoid cuticle lining the 

 azygos oviduct and its apertures to the exterior is very much more distinct than it was ; 

 and a delicate cuticle may be traced in the stem of the receptaculum seminis and the 

 vesicles of the sebaceous glands. The minute cells mentioned before (p. 163) as coating 

 the azygos oviduct, especially the portion between the two external ajjertures, may be 

 traced in a thin coat over the paired oviducts, anterior section of the azygos oviduct, 

 duct of the Inirsa, stem of the receptaculum seminis, duct and vesicles of the sebaceous 

 glands. There does not seem to be any change in the histological appearance of these 

 cells. 



(i) The indirect Union of the Bursa Copulatrix with the Azygos Oviduct, 

 AND THE Development of the Odoriferous Glands. 



The bursa copulatrix has up to this time been in direct union wdth the azygos oviduct. 

 At the close of the preceding stage it assumes, as tigs. 44, 45, PL XVII. show, a 

 position decidedly to the left of the middle line of the azygos oviduct, a change of 

 position which is shared by the tube connecting the azygos oviduct to the anterior or 

 bursal aperture. The connection Ijctween the bursal duct and the oviduct is converted 

 in this stage into a short tube which opens into the azygos oviduct on its dorsal aspect, 

 and into the bursal duct itself laterally. This tube is the future seminal canal. It is 

 shown in fig. 46, PL XVII., and in section in fig. 69, PL XIX. As may be seen from 

 the latter figure, the course taken by it is not horizontal, but obliquely upwards from 

 the oviduct to the bursal duct. Of the two ends of the tube the oviducal is larger than 

 the bursal. In later stages it assumes an S-shaped curvature, and its oviducal end is 

 frequently markedly dilated. It may be noted that the bursal duct proper is now in the 

 same straight line or in direct continuity with the duct which previously led from the 

 azygos oviduct to the anterior or bursal aperture. The duct last mentioned is derived, 

 in the first instance, not from the anterior paired vesicle of the caterpillar, like the 

 dorsal portion of the bursal duct of the imago, but from the azygos oviduct itself. 



xlnother important feature at this period is the appearance of the two odoriferous 

 glands. The posterior or oviducal aperture of the azygos oviduct continues to shift 

 backwards ; it is behind the vesicles of the sebaceous glands and near the anus. 

 Eighteen to twenty sections intervene between it and the bursal or anterior aperture, as 

 compared to four, five, or eight sections, at the assumption of the pupal condition. It is 

 separat from the anus by only six to eight sections. In other words the distance it has 

 gained in one direction it has lost approximately in the other. The odoriferous glands 

 develop as two tubular ingrowths of the hypodermis, one on the right, the other on the 

 left, of the middle line, perfectly distinct one from the other ; that is to say, each of 



