50 Illinois State Laboratory of Natural Histortj. 



are obliterated on the gland-bearing somites. In some cases 

 the gland is developed only on the posterior part of the wall of 

 somite 13, and it is generally less developed on this somite than 

 on those which succeed it. It is not developed over a narrow 

 median ventral area between the two inner rows of seta3. The 

 lateral edges of this area are sinuous, from ingrowths of the 

 gland between each two pairs of setfe. The area begins to 

 widen towards the front on somite 14, and towards the reax 

 on somite 17. 



The External Apertures of the Genital Organs. 



The external apertures of the three pairs of spermathecae 

 show very clearly in examples killed in corrosive sublimate, at 

 the anterior edges of somites 7, 8, and 9, opposite the inter- 

 spaces between the setge of inner pairs on the same somites. 

 The openings are upon minute transversely-placed prominences. 



The external apertures of the oviducts are two minute 

 pores, very close together, within and a little in advance of 

 the two inner pairs of seta on the ventral side of somite 14. 

 In many examples the surrounding integument is a little ele- 

 vated, producing a low transversely-elongated mound bearing 

 the apertures at its summit. 



Two copulatory papillae are usually present on the posterior 

 edges of somites 17 and 20, one opposite each inner pair of 

 seta? of these somites. In most cases these are the only 

 papilUe present; but in one example seen, there were besides 

 the pair on somite 17, four pairs on somites 20, 21, 22, and 23, 

 respectively. In still other examples a pair was found on each 

 of somites 16, 17, 20, and 21. 



At about the middle of somite 18, at the points at which 

 the pairs of copulatory seta^ appear, are the anterior ends of two 

 shallow copulatory fossiu shaped like parentheses, but with the 

 convex sides towards each other. These grooves extend across 

 somite 19 and terminate on somite 20, where also copulatory 

 seta; appear. No apertures of sexual organs can, by ordinary 

 means, be perceived in this region; but on cutting out the body- 

 wall and studying it with a microscope, the aperture of the 

 duct of a prostate gland will be found in the two extremities 



