206 CALIFORNIA ACADEMY OF SCIENCES. 



latter contains a second thicker and more chitinous 

 tube and a chitin rod. The rod arises posteriorly from 

 the inner tube. Between the outer tube and the mus- 

 cles on the dorsal side of the former lie the forward- 

 running parts of the vasa deferentia. These enter the 

 muscles posteriorly and then pass into the upper part 

 of the cavity within them, run forward to the anterior 

 end of this, and then emerge to join soon the seminal 

 vesicle. The inner tube and rod pass forward some 

 distance beyond the anterior end of the outer tube, and 

 the former is thrown into several convolutions which 

 vary in different specimens. The anterior longitudinal 

 muscles arise from the anterior end of the mass of trans- 

 verse muscles and converge upon the tip of the chitin 

 rod. From these a small band of fibers continues into 

 the thorax, where it is attached to the floor of the meta- 

 thorax in the middle line. The transverse muscles, when 

 detached from the ventral plate, but left with their 

 upper ends still joined to the vertical membrane, have 

 very much the appearance of a bunch of fire-crackers, 

 the fold of membrane representing the axial fuse. 



The inner tube on account of its being more strongly 

 chitinous than the other appears dark, while the outer 

 is transparent. The interior of the inner tube is beset 

 with numerous chitinous projections. In the posterior 

 part these are of the form of small conical processes 

 closely distributed over the walls. Somewhat farther 

 forward they increase in length and form sharp back- 

 ward-pointing teeth. Still farther in front they become 

 much more elongated, and anterior to these they take the 

 form of large backward-projecting, spike-shaped ap- 

 pendages having sharp points, and they almost obstruct 

 the lumen of the tube. Beyond these a decrease in size 

 of the processes takes place, and in the walls of the 



