166 PROF. W. H. JACKSON ON THE 



them has its own separate aperture to the exterior. The ingrowths are in front of or 

 anterior to the oviducal aperture, between it and the bursal aperture. They are near 

 the oviducal aperture and underlie the anterior margin of the vesicles of the sebaceous 

 glands. One of them is shown in fig. 74, od.gl., PI. XIX. 



Two points of minor interest may be noted. The stem of the receptaculum seminis 

 constantly bears near its entrance into the azygos oviduct a minute pyriforin vesicle 

 (PL XIX. fig. 70). This vesicle is evident to the naked eye in dissections belonging 

 to later stages. It is not present in the imago, and it represents transitorily the 

 pyriform capsula seminis of Pieris and many other Lepidoptera, which is replaced, 

 functionally at least, by irregular dilatations of the receptaculum in Vanessa. 



The second point is the almost complete disappearance of the furrow in the ventral 

 hypodermis corresponding to the ventral furrow in the chitinoid cuticle crossing the 

 eighth and ninth sternal regions. The hypodermic cells themselves are of much 

 diminished vertical length, and very readily separate from the pupal cuticle. On their 

 outer surface is a darkly staining layer looking like a new cuticle. It is, I believe, a 

 coagulable fluid, for in the next stage it is increased in amount, and in some of the 

 sections the growing scales may be seen imbedded in it. There is also a curious median 

 ridge of elongate hypodermic cells (PI. XIX. fig. 71) running forwards for a short 

 distance from the bursal aperture, which is now a deep funnel-shaped cavity. The cells 

 of this ridge appear eventually to secrete the thickened glass-like chitin of the globular 

 body covering the entrance to the bursal aperture ; see p. 150, ante. 



(5) The Formation op the Terminal Abdominal Papilla. 



At the commencement of this stage, in specimens, that is to say, 24 to 36 hours older 

 than the last described in the previous stage, the two odoriferous glands have increased 

 in length, their apertures have approached one another medianly, or to put it in other 

 words, and perhaps more correctly, the hypodermis forms a prominent ridge to the 

 outer side of both apertures, so that they open into a common depression or pit. To 

 the right and left of this depression there is a slight infolding of the hypodermis ( X ), the 

 first indication of the formation of the terminal abdominal papilla. These facts are 

 shown in the section drawn PL XIX. fig. 75. The infolding becomes a little deeper 

 in sections following the one figured and taken from the same specimen (PL XIX. 

 fig- 77, X). 



In specimens about 24 hours older still, the changes thus described are much more 

 conspicuous. The apertures of the two odoriferous glands are more deeply placed, and 

 there appears to be a very short common vestibule, as may be gathered from the section 

 figured (PL XIX. fig. 76). The condition of the parts closely approaches that which 

 obtains in the imago. The lateral infoldings of hypodermis to form the terminal 

 abdominal papilla are deeper, much more so indeed further back, as may be seen from a 

 section through the anus (PL XIX. fig. 78, x)- The oviducal and anal apertures are 

 now so close together that the latter is cut through two sections behind the former. It 

 may be added here, to point the contrast, that the anal aperture at the commencement 



