490 Mr. E. E. Prince ow the Nest and 



crossing over the intestine from the right to the left side 

 (PI. XIV. fig. 6, 5), and after a short parallel course passing 

 on the ventral side of the intestine to the right side again 

 (PL XIV. fig. 6, c), debouching behind the genital pore 

 (PL XIV. fig. 6, d) into a urinogenital sinus, forming the 

 posterior portion of a cloacal depression (PI. XIV. fig. 6, e), 

 into which also the anus opens (PL XIV. fig. 6, /) . The wall 

 of the bladder consists of two layers, an internal epithelium 

 (PL XIV. fig. 1 B, a), which is readily detached, and a 

 dense external connective layer (PL XIV. fig. 1b, J), which 

 thins out as the bladder enlarges anteriorly. Traces of an 

 intermediate muscular layer appear posteriorly where the 

 walls are extraordinarily thickened. The descending ureters 

 (PL XIV. fig. 1 B, c c) approach opposite sides of the 

 bladder, that on the left proceeding obliquely below the 

 common duct of the vasa deferentia, and passing forward 

 and merging in the walls of the bladder on the left side. This 

 union is shown in the same transverse section which shows 

 the union of the vas deferens of the left testis with that of the 

 right. The course of the right ureter is shorter and more 

 direct, as the bladder lies on that side of the abdominal cavity 

 at this point. It coalesces with the right wall of the bladder 

 precisely opposite the left ureter. K^ the bladder descends 

 to cross the intestine inferiorly it twists, so that the left 

 ureter is brought to the ventral side and the right ureter 

 ascends to the dorsal side of the cervix of the bladder. Both 

 return to the lateral position as the bladder crosses the intes- 

 tine. The intestine now curves to the right, and the relations 

 of the ureters become reversed, the right being below and the 

 left rising to the dorsal side of the bladder. They increase 

 rapidly in capacity, showing in cross section an extremely 

 elliptical cavity, and as the bladder enlarges they pass 

 obliquely into its chamber, their walls being continuous with 

 the external layer of the bladder. Along this tortuous course 

 the viscid secretion of the renal tubules reaches the bladder, 

 where it is stored up. When first formed the secretion is 

 simply a plastic jelly ; but a fibrillar structure appears to 

 rapidly develop in it. Indeed this appearance is assumed 

 while the secretion is contained in the ureters. The epithelial 

 cells of the urinary canals exert so actively the secreting func- 

 tion that the bladder becomes much distended by the accumu- 

 lating mucus, and at length it flows slowly to the urinary 

 aperture, where it emerges as a tenacious elastic thread which 

 readily adheres to any external object on contact. It can 

 hardly be doubted that this secretion can be extruded at 

 pleasure, the walls of the bladder assisted by the abdominal 



