2l6 L. M. HICKERNELL. 



wards through the series of nymphal stages where structural 

 variations are relatively slight, as between two successive stages, 

 than to jump from the adult condition back to the earliest nymph 

 and then work up to the adult condition once more. It is be- 

 lieved that a description of these different stages in reverse order 

 is warranted in the present instance in view of the circumstances 

 outlined above. 



The alimentary tract in nymphs of 21-24 mm - length has the 

 same general arrangement of parts as is found in the adult. The 

 form and structure of the individual organs varies, however, 

 in some respects. The posterior crop (Fig. I, pc) always has its 

 walls wrinkled and contains a tortuous lumen, as if the structure 

 had collapsed completely, while in the adult this division possesses 

 smooth, thin walls surrounding an enormous lumen. The size 

 relations of some of the other parts also vary as is shown here- 

 after. A general view of the entire system as seen from the left 

 side is represented in Fig. I. The esophagus is a simple tube, 

 uniform in diameter, and leads into the anterior crop (ac). The 

 latter with its dorsal adherent "internal gland," is of about the 

 same relative size as it is in the adult. The anterior crop empties 

 through a narrow opening into the posterior crop (pc). The 

 latter is greatly unlike the corresponding division in the adult. 

 Its relative length is much the same but its walls are uniform in 

 texture and much folded throughout. In the adult the walls of 

 the organ are distinctly variable in thickness and are not folded 

 to any extent except at the extreme anterior end where the caecal 

 projection runs ventral to the anterior crop. The outer surface 

 of the posterior crop is closely apposed on all sides by fat. This 

 probably has something to do with the collapsed condition of the 

 tube in this region. At any rate, its opposing walls almost touch 

 each other throughout its whole extent, thereby making the 

 lumen narrow and irregular (Fig. 4, pc). 



The ascending intestine is relatively larger in diameter in the 

 21-24 nim. nymph than it is in the adult. Its general course and 

 connections are the same as in the adult but its size, both ex- 

 ternally and with respect to its lumen is noticeably greater (Figs. 

 I and 4, at). The ascending intestine enters the internal gland 

 in the same fashion as it does in the adult. The descending 



