172 PKOF. W. H. JACKSON ON THE 



receptaculum seminis, azygos glands, &c.) are at first paired. The azygos efferent 

 apparatus of Insects must therefore he deemed as morphologically a secondary and more 

 complicated form. 



(5) The male and female efferent ducts are strictly homologous. 



(0) The cavities of the oviducts, uterus, vagina in the female, of the vasa deferentia, 

 appended organs and ductus ejaculatorius of the male arise independently and come into 

 connection secondarily. 



My own ohservations on Vanessa lo, which are, however, limited to the female, 

 support Nusshaum's conclusions in most particulars. The larval oviducts which seem to 

 come from the same embryonic rudiments, as do the ovaries themselves, are converted 

 into the paired oviducts of the imago, whereas the rest of the efferent apparatus with its 

 appended organs is derived from the hypodermis. The hypodermis, however, only gives 

 origin to the epithelium of the organs ; their connective and muscular tissues spring 

 from other cells which appear to be contained in the coelomic fluid or blood. The 

 rudiment from which the bursa copulatrix and receptaculum seminis are derived is 

 distinctly paired in Vanessa, more so in Pieris brassier, and most of all in Phalera 

 bucephala, where the two parts are at first entirely separate. The paired character of 

 the rudiment is lost, and then the bursa and receptaculum grow out, not from opposite 

 sides, so that one of them might be considered as an organ belonging to the left side of 

 the body, the other to the right, but from opposite ends, a very remarkable feature ; 

 consequently neither of them belong to one or other side of the body, but both equally 

 to both sides, if regard be had to the primitive condition of the rudiment. Similarly the 

 sebaceous glands, which are paired, are derived from the dorsal portion of a paired 

 rudiment, the two parts of which are widely separated in Phalera bucephala. In these 

 organs, however, the paired character of the rudiment is persistent, and the only fusion 

 that takes place is in the portion which forms the vesicles of the sebaceous glands and 

 the single duct that leads from them to the azygos oviduct. 



The azygos oviduct itself, however, is not paired either primitively or at a later period, 

 unless the posterior extremity derived from the basal portion of the posterior vesicles 

 may be considered as paired in the first instance. In this respect the development of 

 the organ in Vanessa contrasts with the conclusion formulated by Nussbaum. At the 

 same time it agrees with the simple character of the vaginal rudiment in Aphis and 

 some other Insecta ; only it must be borne in mind that in the Butterfly it is, as will be 

 pointed out presently, a portion only of the anterior section of the azygos oviduct that is 

 really homologous with the vagina of other Insecta, and this portion, as it happens, 

 differs, in part at least, in its mode of development from the rest of the azygos oviduct. 

 Moreover, and this is a second point of difference, the cavity of the azygos oviduct of 

 Vanessa is from the first in connection with the cavities of the rudiments of both bursa 

 and receptaculum and of the sebaceous glands. This is not true, however, with respect 

 to the paired oviducts. They are at first solid ; their cavities when formed are inde- 

 pendent and only come into connection at a later period with the cavity of the azygos 

 oviduct, facts enfirely in accordance with Nussbaum's statement on the same point. 



