THE MID-INTESTINE OR "STOMACH" 



315 



into the end of the mid-intestine (" stomach "). The latter also is 

 sometimes lined with an. intima. The limits are also determined 



by a circular projection, directly 

 behind which is an enlargement of 

 the intestine in the shape of a 

 trench (rigole), or circular cul-de-sac 

 (the "pyloric valvule" of some 

 authors, including Beauregard), 

 while the walls of the small intes- 

 tine contract so as to produce a 

 considerable constriction of the cavity of the canal. 

 This constriction exactly coincides with the beginning 

 of the double layer of circular muscles in the wall of 



mD 



eD 



FIG. 318. Digestive canal of Meloe : sch, oesophagus ; A7, oesoph- 

 ageal valve ; mD, mid-intestine ; eD, hind-intestine ; Ei, eggs ; g, 

 sexual opening. After Graber. 



the small intestine. An internal layer, 

 which is the continuation of the cir- 

 cular muscles of the chylific stomach, 

 and an external layer much more 

 developed probably belong to this 

 part of the alimentary canal. Since 

 the homologue of the circular fold 

 occurs in the locust as well as in 

 Diptera, it is probably common to 

 insects in general. 



Gehuchten adds that the limit set by the 

 circular projection does not exactly coincide 

 with the opening into the intestine of the 

 urinary tubes and the two annexed glands. 

 He shows by a section (his Fig. 133) that the 

 tubular glands open into the alimentary canal 



FIG. 31 1. Digestive canal 

 /, gizzard or proventriculus ; k, 



of Carabus monilis : h, oesophagus; 



., B _ r , , stomach," with its cceca (/); p, urinary 



tubes";"?, "the'ir point of insertion ; m, , colon, with coccal glands ; *, anal 

 glands ; a, b, a, a gastric ccecum ; a, b, portion of Hning of gtaard. After 

 Newport. 



