1918] Alinu'iilary CaiiaJ of Altica Larva 299 



the ileum and, like the latter, it does not stain either with eosin 

 or Delafield's hasmatoxylin ; the intima in the bladder is some- 

 what thinner, and the primary intima is not pigmented. The 

 epithelium of the two portions is continuous; the cells of the 

 ileum are more elongate than those of the bladder, but the 

 nuclei are of about the same size. The basement membrane is 

 continuous. The peritoneum, which ends when the circular 

 muscles grow out and surround the bladder, is continuous with 

 the connective tissue sheath in which they are lodged. 



There is no suggestion of an urethra, or stalk, leading from 

 the bladder to the intestine, such as is often present, except 

 that two of the undulatory folds of the iliac epithelium are 

 larger where the bladder empties, and make a sort of passage- 

 way between the two lumina. Since such a stalk is present at 

 least in A. nemorum (Schindler 1878; p. ().31), this may represent 

 the first step in the development of one. 



The fusion of the four vessels is shown in figure 17; the 

 fusion of the lumina of the two outer vessels, in figure 18; the 

 complete bladder, in figure 19; and the junction of the bladder 

 and ileum, in figure 20. 



THE DISTAL PORTION OF THE ILEUM. 



Transition. As soon as the bladder has emptied into the 

 canal, the intima is gradually reduced in thickness, and the 

 epithelial cells become thicker, with the folds larger and less 

 acute; the nuclei also become larger, and the cytoplasm tends 

 to become differentiated into two regions, as is explained below. 

 This transition is gradual, not abrupt. All of the layers of the 

 proximal portion of the ileum are continuous with those of the 

 distal. 



Intima. The intima is divided into a primary and a sec- 

 ondary intima, but the latter is much thinner than in the 

 proximal portion. It becomes progressively narrower through- 

 out this region. 



Epithelium. The epithelium is composed of large, irreg- 

 ularly cuboidal cells, whose boundaries are frequently so indis- 

 tinct that they form an apparent syncytium. In most cases 

 there are two areas of cytoplasm clearly distinguishable: an 

 inner (toward the basement membrane) layer, denser and darker, 

 staining violet-pink with eosin, and an outer, more or less 



