DIGESTIVE SYSTEM OF PERIODICAL CICADA. 2iy 



intestine also emerges from the complex of tubes as it does in 

 the fully developed insect. 



The descending intestine is relatively smaller in this stage than 

 it is in the adult condition. Emerging from the internal gland it 

 runs in a general posterior direction as in the adult, finally making 

 a knot or coil (Fig. I, kk) just before emptying into the rectum. 

 There are some variations in the histological structure of the 

 epithelium in its walls but the tube is easily recognized in section 

 when one is familiar with its microscopic structure in the adult. 



The rectum does not differ greatly from that in the transformed 

 insect. It receives the descending intestine and then gradually 

 narrows until the anal opening is reached. 



Among the younger nymphs there are variations in size and 

 arrangement of the digestive organs but these are slight as com- 

 pared with the structural differences shown between the organs 

 of the early nymphs and those about to transform to the adult 

 condition. In nymphs of 14 mm. and 7 mm. body-length there 

 is not enough variation in the arrangement of the organs in the 

 two stages to warrant separate description. Figure 2 is based 

 upon specimens of 14 mm. length but, except for size, the same 

 figure applies to the shorter and younger stage. Esophagus, 

 anterior crop, and internal gland are practically the same as in 

 the stage previously described. The remaining portions of the 

 system, however, differ greatly in many respects. 



The posterior crop does not have any suggestion of saccular 

 structure in these early stages. Its walls are folded as in the 

 other previously described specimens but it does not assume the 

 enormous diameter common to that division in the older nymph 

 and adult. In fact, the ascending intestine has a larger diameter 

 in this stage than does the posterior crop. Its course is almost 

 straight through the center of the body until it reaches a point 

 just anterior to the rectum. Here it joins the ascending intestine. 



The ascending intestine (Fig. 2, a/) is exceedingly prominent 

 at this time. It is much convoluted and extends posteriorly 

 in the region of the rectum, from which place it runs anteriorly. 

 For the most part it runs along the ventral surface of the body 

 and when it reaches the internal gland it disappears as in the 

 adult. The interweaving of the posterior crop and the two 

 intestinal divisions seems difficult of interpretation when first 



