30 THE EARLY STAGES OF TABANID^ 



auditory capsules is developed, which Graber distinguishes as oto- 

 cysts without cilia (aciliate) from other known otocysts (ciliate 

 otocysts). 



The organs were found by Graber (Spring, 1878) on a dipterous 

 larva collected with other material, on the bottom of a mud pond 

 in a brick factory. The larva (Plate 9, Fig. 103) was when extended 

 about 40 mm. long, cylindric, strongly spindle-shaped, and pointed 

 at the end, and except the dark intestinal system, of an almost glassy 

 transparence. Eleven segments were counted, which with the ex- 

 ception of the terminal ones, were surrounded by a girdle of papilli- 

 form retractile processes. Unfortunately, as literature was not acces- 

 sible, the species could not be determined. 



In order to see the organ in the fresh condition, the larva is laid 

 on its ventral side and fastened with an elastic holder. The organ 

 (Plate 9, Figs. 104 to 108) lies in the median line of the dorsal side, 

 behind the termination of the dorsal blood vessel, and immediately 

 behind the border incision between the ninth and tenth segments. 

 By focusing from above, at first the body cuticle becomes visible, 

 which derives from the presence of longitudinal ridges the extra- 

 ordinary elasticity characteristic of these larvae. When focusing 

 farther down, the epithelium is seen, consisting of flat polyhedric 

 cells, and following this a network of pale lobes and trabeculae with 

 dendritic tracheal expansion; namely, the fat body. Immediately 

 underneath these tissues lies the organ in question, which is conse- 

 quently completely separated from the integument. It consists of 

 a pale capsule 0.3 mm. in length and pear-shaped, its free and broader 

 end directed upwards, while its pointed hind end is prolonged into a 

 narrow tube. The capsule being of considerable size is visible even 

 at slight magnification. Moreover, it is not likely to be overlooked 

 because of the intensely black bodies included in it, which strongly 

 contrast with the light background. 



In detail the structure of the organ appears to be peculiar. From 

 the capsule proper with its tube the nerves and muscles attached to its 

 anterior end may be distinguished. The whole capsule together with 

 the terminal tube appears, as Graber says, to be a cecum-like in- 

 vagination of the ectoderm. Unfortunately the origin of the ter- 

 minal tube could not be found by Graber; it apparently lies in the 



