1891.] MIOKOSCOPICAL JOURNAL. 247 



.35 mm. by .5 mm., this lying with the broad end backward. From 

 the narrow anterior end of this third cavity passes a slender tube about 

 .2 mm. long by .05 mm. wide, which opens into the point of converg- 

 ence of the eight large coeca, and from this point extends another simi- 

 lar tube, which rapidly enlarges into the sub-spherical vestibule of the 

 Malpighian tubules. The cosca, radially arranged, are about .12 mm. 

 in diameter, and average 1.5 mm. in length. They are straight, or 

 slightly contorted, with smoothly-rounded ends, and are nearly filled, 

 when in normal condition, with large, pale, loosely-attached, subspheri- 

 cal cells, similar to those of the gastric epithelium, but containing m i^e 

 fatty granules. These cells are variable in size, and individual ones 

 become greatly swollen, and probably break down in secretion. The 

 lumen of the tube is an irregular linear space, not readily distinguish- 

 able in the midst of the cells. 



The Malpighian vestibule is a nearly spherical dilatation of the canal, 

 immediately behind the ccEca, about .45 mm. in diameter, the epithe-* 

 Hum of which resembles that of the greenish tubules. The latter are 

 four in number, about .r mm. thick, and go off at equal distances in 

 a radial manner. The Malpighian vestibule opens directly into the 

 short, broad, thick-walled rectum. There is no chitinous cuticular 

 lining in any portion of the alimentary canal except the rectum and the 

 CESophagus. 



The principal peculiarities of this anatomy are the subdivision of the 

 Stomach into three compartments — a rather unusual feature in insects 

 of this relationship — the shortening of the posterior part of the digestive 

 tube with the entire absence of any tubular portion, and the develop- 

 ment of the large coeca, possibly as a substitute for the last — a pecu- 

 liarity otherwise quite unknown to me in any hemipterous insect. 



Cui'iously enough, the disease in question is strictly confined to the 

 whorl of coeca above described, and in them has finally the effect to 

 completely destroy the secreting epithelium, the cells of which break 

 dovv^n and disappear, leaving the delicate tubules filled with a vast mass 

 of microbes with some small intermixture of droplets of fat and a little 

 nondescript debris^ the result of cellular decomposition. The bacterial 

 mass is always a perfectly pure culture of Micrococciis insectoi-um^ 

 Burrill, described in 1883 from the alimentar}' canal of the chinch-bug, 

 and not since encountered elsewhere. This microbe is usually oval, 

 with narrow ends, oftenest in couples, but sometimes in strings of four, 

 six, or eight. When in strings it is likely to be shorter and more 

 abruptly rounded at the ends. Sometimes elongate forms are seen, 

 about twice the typical length, with no appearance of division — proba- 

 bly individuals in process of multiplication. It takes the aniline stains 

 uniformly, never presents flagellate motion, and never forms spores. 

 Undivided segments vary from .8 to 1.6 ij- in length, with a uniform 

 width of .65 IJ.. 



In slightly affected bugs it is found within the cells of the coeca, the 

 nuclei of which may become crammed with it; but even after the com- 

 plete degeneration of this epithelium the other cells of the alimentary 

 tract are almost absolutely free from it — a fact which can only be ex- 

 plained on the supposition that it is select in its conditions of growth. 

 In bad cases it may be found free in the fluids of the posterior part of 

 the canal, but not in number to compare with those in the ccEca. In 



