164 PEOF. W. H. JACKSON ON THE 



stage tlie oviducal aperture is placed well iu front of the anterior tubular end of the 



sebaceous portion {cf. p. 185 on fig. 65), which is separated throughout its whole extent 



on the ventral aspect from the hypodermis, the space between the two being occupied 



by intrusive fatty tissue. The two tubular portions, the future glands, lie parallel to 



one another, are sharply arched and curved upon themselves, and the portion common 



to them at their point of origin is flattened dorso-ventrally, of fair lateral extent, but of 



no great length (PL XIX. figs. 65, 66). As development proceeds the tubes show a 



o-eneral increase in size, become a little tortuous, but continue to be curved upon 



themselves. The common basal portion is a little shorter, slightly dilated on each side ; 



the oviducal aperture is more directly beneath it, and consequently the tubular antei'ior 



portion of the gland apparatus is nearly vertical and somewhat confused with the azygos 



oviduct, as is seen from the sections PI. XIX. figs. 67, 68. All the changes just 



detailed are more and more accentuated by degrees. The gland-tubes diverge from one 



another laterally and are directed backwards, but as they lengthen, curve forwards at 



their apices. The common basal portion is distinctly separated into a right and left 



dilatation, connected as sections show {cf. figs. 67, 68) to the azygos oviduct by a 



short and distinct tu.bular duct hidden in the vertical view beneath the common basal 



portion. The oviducal aperture is now placed immediately below or slightly behind the 



common basal portion of the gland tubes. Finally, as may be seen from PI. XVII. 



fig. 44, the duct {d.v.gl.) connecting the two dilatations or vesicles of the sebaceous 



glands to the azygos oviduct lengthens out, and the azygos oviduct itself extends 



backwards {p.od'.), carrying its aperture, i.e. the oviducal or posterior aperture, with it. 



As to the azygos oviduct. At first, that is to say at the time corresponding to fig. 38, 



PL XVII., no change of any noticeable degree is obvious from what obtained at the 



close of the preceding stage. Its anterior or bursal aperture lies just below the bases of 



the bursal and receptacular outgrowths (PL XVIII. fig. 55 d), its posterior or oviducal 



aperture is just at the anterior end of the sebaceous apparatus (PL XVIII. fig. 55/). 



Both apertures are very minute and very close together. At the time corresponding to 



fio-. 40, PL XVII. , its anterior extremity is still solid, but the portion in front of the 



bursal aperture is rounder in cross section than it was, and separated by a greater 



distance from the hypodermis, fatty tissue intervening. The portion of the azygos 



oviduct behind the bursal aperture and in front of the oviducal aperture is now clearly 



separated from the hypodermis by a space filled with intrusive fatty tissue (PL XVII. 



fi". 41). The oviducal aperture itself is nearly directly below the base of the sebaceous 



vesicles. At the close of this stage the bursal aperture is connected by a tubular duct 



(PL XVII. fig. 45) to the azygos oviduct, and the oviducal aperture is still farther 



back, situated well behind the base of the sebaceous vesicles (PL XVII. fig. 44, 



p.od'.). 



The paired oviducts increase in size, and at the period to which fig. 40, PL XVII. 

 belongs have acquired a distinct lumen (PL XIX. fig. 60). The lumen is a fine 

 channel which appears to extend ventrally, or in other words it develops in a direction 

 proceeding from the ovary towards tHe azygos oviduct. It never communicates Avith 

 the latter until the parts have assumed the size and proportion shown in figs. 61, 62, 



