MOEPHOLOG-T OF THE LEPIDOPTEROUS PUPA. 199 



Mr. White spent a great deal of time and trouble in examining pupa? and putting aside the 

 most favourable specimens for my use. I owe the specimens from which the following 

 figures were made to his kind assistance : — Plate XX. fig. 26 ; Plate XXI. figs. 9, 12, 

 13, 24, 25, 30, 34. Plate XXI. figs. 1, 2, 28, and 29 were drawn from Professor 

 Meldola's ^material. Pigs. 1 and 2 represent two especially favourable individuals 

 selected after the comparison of a very large number. 



2. The Male External Reproductive Organs. — A casual examination of a large pupa with 

 the naked eye, or of a small one with the assistance of a low raagnifying-power, at once 

 shows the existence of two convex or flattened, roundish, oval, or trianguloid tubercles, 

 placed one on each side of the middle venti*al line, in the ninth abdominal segment. 

 Careful examination throws some doubt upon the certainty of this segmental relationship. 

 There is no doubt, however, that the organs always occur in the zone of the ninth 

 abdominal, viz. in an area which would be included in the segment if the boundaries of 

 the latter were produced in the direction indicated by their course in the dorsal and 

 lateral regions. Between the tubercles is a furrow which generally becomes a deep pit 

 in its central part ; this pit is the ancient opening of the pupal vas deferens, and it 

 now corresponds externally to the termination of the ducts internally. 



It is furthermore possible by carefully selecting the pupse, to find individuals which 

 approach the condition of a perforate orifice. I have found Smerinthus populi the 

 best species for this pui*j)ose, and on examining the organs from the inside of the 

 empty pupa-case of a favourable individual, the lips of the depression are seen com- 

 pletely introverted, their internal surface having the black appearance and peculiar 

 roughened texture which is characteristic of the exterior of the pupa, and with which it 

 is of course continuous. The surface of the introverted funnel-like opening is covered 

 with the same lustrous white layer which invests the whole interior of tlie cuticle, and 

 which therefore is contrasted very sharply with the internal surface or lumen of the 

 funnel. In this case the funnel is not closed at its deepest point, the lumen being 

 obstructed a little higher up by the fusion and hardening of the semifluid substance into 

 a solid plug immediately after pupation. When looked at from within, the sides of tlie 

 sharply truncated funnel are quite free, recalling most vividly the condition in which 

 the lumen was perforate throughout. The whole appearance from within, in fact, singu 

 larly resembles that of one of the superficial functional spiracles looked at from the same 

 point of view. These have similar introverted lips, also sharply truncated, and sliowing 

 the characteristic black surface which lines the lumen. The rudimentary eighth abdo- 

 minal spiracle, on the other hand, is completely closed below, and the white surface lining 

 the pupal cuticle is unbroken over it. It is very remarkable that this most ancestral 

 generative organ should in certain cases retain such strong indications of the time when 

 it was functional. 



On the other hand, there are proofs of the ancestral nature of the male organs, and of 

 their rudimentary condition, as far as the pupa itself is concerned. Thus the individual 

 differences are very great in position and form, and in the degree to which the structures 

 are developed. Purthermore, these organs are often asymmetrical when all other parts 

 of the pupa are entirely normal. The asymmetry may be slight, as in Plate XX. fig. 11, 



