624 



l)ut the spiracles of th<^ eighth somite are abortive and the tenth somite 

 bears the cremaster, the homologue of the anal valve Riley, Jack- 

 son'. The sustentors which are present on this somite in some Lepi- 

 (loptera are held by Riley to represent the »plantae« of the anal pro- 

 legs, but it appears to me that they and the sustentoral ridges represent 

 the body of the tenth somite and that the anal prolegs of the cater- 

 pillar are replaced by the two rounded elevations one on either side 

 the anus. The abdomen of the imago is composed apparently of nine 

 somites. The first seven have stigmata : the eighth which has the aper- 

 ture of the bursa copulatrix on its ventral aspect has lost its stigmata 

 or only shows a trace of them as slight scars. The terminal papilla or 

 »ninth somite« of the abdomen is conical, and contains the anal and 

 oviducal apertures. It is, I find, produced in Vtmessa Io at a late 

 period of pupal life by the ingrowth of a fold of hypodermis surround- 

 ing the anus and oviducal aperture : the latter shifts backwards in 

 development. It must be regarded as a new formation, at least in the 

 species named, in the tenth pupal somite, the rest of the tenth somite 

 and the whole of the ninth being merged in the membrane between 

 the base of the papilla and the eighth somite. 



Herold in his )> Entwicklungsgeschichte der Schmetterlinge« 

 published in 1815, has given an account of the mode in which the 

 female organs develop in Pontia brassicac from the close of larval life 

 and during the pupal period. His results briefly summarised are as 

 follows. The paired larval oviducts are attached in the full grown 

 caterpillar to the posterior edge of the seventh abdominal somite near 

 its centre — a fact confirmed by Vessels (Zeitschr. f. wiss. Zool. 

 XVII, 1867, p. 561). Their ventral ends are connected by two striated 

 bands crossing the eighth sternal region to a pair of oval pieces in the 

 ninth sternal region. Subsequently the larval oviducts and two oval 

 pieces approximate and fuse. The ventral ends of the larval oviducts 

 unite and form the azygos portion of the oviduct whilst the oval pieces 

 give origin to the bursa copulatrix, to the unpaired gland (= recepta- 

 culum seminis of von Siebold) and to the paired glands. He does 

 not account for the presence of the two apertiires to the female organs 

 in the imago. 



My own investigations have been conducted almost entirely on 

 Vanessa Io because I was unable to command at the time a sufficient 

 supply of Pontia hrassicae. The results may be summarised to the 

 following effect. 



1) The larval oviductts are attached as st;itc(l ])y Herold and 

 Bessels. The fully grown caterpillar has a pair of vesicles invaginated 

 from the hypodermis in the eighth sternal region and a second pair in 



