170 PKOF. W. H. JACKSON ON THE 



ninth sternum, and the ventral portion of the tenth somite of the pupa anterior to the 

 place of origin of the terminal papilla. 



(10) The eighth pair of abdominal spiracles is abortive in the pupa and is lost in 

 the imago. The other seven pairs of abdominal spiracles persist. 



(11) There is a cuticular secretion, apparently fluid, formed by the hypodermis just 

 before the appearance of the scales. 



There are a few points as to which further investigation or confirmation is necessary. 

 They are the following : — the nature of the band contained in the posterior filaments 

 attached on the one hand to the rectum, on the other to the posterior paired vesicles of 

 the caterpillar ; the exact mode in which the anterior section of the azygos oviduct 

 originates ; the way in which it becomes connected to the paired oviducts whether by its 

 growing up to them, or by their growth uniting them to it; the details of the histolo- 

 gical process by which the posterior oviducal aperture shifts backwards ; the character 

 of the secretion found in the later stages (4 and 5) between the hypodermis and the 

 pupal cuticle. These various points I hope to determine in the course of next summer. 



General Conclusion. 



The uniformity which prevails in the structure of the genitalia of the Lepidoptera at 



large, so far as concerns essential features, is so great in the species that have been 



examined, that it warrants the assumption that a similar uniformity will be found to 



obtain in the mode in which they develop. It is true that Herold has given a very 



different account of the development as observed by him in Pieris brassicce to what is 



stated in the foregoing pages. He has stated that the paired and azygos oviducts in 



that Butterfly are alike derived from the paired larval oviducts, and that the bursa 



copulatrix, receptaculum seminis, and sebaceous glands are all outgrowths of a common 



rudiment placed at the anterior margin of the ventral region of the ninth somite. 



Suckow's account of the development of the organs in Dendrolimus pini is identical in 



all essentials. But an examination of several full-grown female caterpillars of Pieris 



brassicce has shown me that the very same rudiments are present in them as have been 



described in Vanessa Io in the present paper. So, too, the full-grown female caterpillar 



of Phalera bucephala and a one-day old female pupa of Sphinx ligustri have parts 



exactly similar to what are shown in PL XVII. fig. 33 in Vanessa Io. There can be 



little doubt that Herold's and Suckow's descriptions are erroneous, and that a fair 



uniformity prevails, at least in the Macro-Lepidoptera, in the mode in which the accessory 



female sexual apparatus develops. 



It is a remarkable fact that very little has been done to elucidate the mode of origin 

 of the secondary genital ducts and their appended accessory organs, either in the male or 

 female, in different orders of Insecta *. Balbiani asserted in 1872, but in general terms 



* Addendttm. — The statement in the text refers solely to developmental data. The presence of a chitinoid cuticular 

 lining appears to constitute a safe anatomical criterion for the purpose of differentiating the portions of the sexual 

 apparatus derived from cpiblast or hypodermis from those which are not so derived. See on the subject, as treated 

 from a comparative-anatomy point of view, Palmen's work ' Ueher paarigo Ausfiihruugsgiingo der Geschleehts- 

 organe hei Inseeten : ' Leipzig, 18S4. 



