GENERAL ORGANOLOGT. 



105 



sac whose closed end unites with the likewise closed posterior part 

 of the archenteron (now called also mesenteron or mid-gut) until 

 the separating wall disappears, whereupon mid- and end-gut com- 

 municate with each other, and the digestive tract becomes a canal 

 extending through the entire body. 



Divisions and Appendages of the Digestive Tract. The part 

 which the archenteron takes in comparison with the ectodermal 



FIG. 59. 



FIG. 60. 



FIG. 59. Bee-larva just after hatching : seen from the ventral surface. The diges- 

 tive tract consists of three portions; a, fore-gut; m, mid-gut; e, hind-gut (not yet 

 connected with the mid-gut) ; sg, limits of segments ; st, stigma ; t, trachea ; n, 

 ventral nerve-cord. (After Butschli.) 



FIG. 60. Digestive tract of the domestic fowl, a, oesophagus ; b, crop; c, glandular 

 stomach; d, gizzard ; e, liver ; f, gall-bladder ; gr, pancreas ; ft, t, small intestine; 

 fc, caeca ; J, large intestine ; m, ureters ; n, oviduct ; o, cloaca. 



proctodseum and stomodaeum in making up the completed diges- 

 tive tract is very different in the various groups. On one side the 

 Crustacea, on the other side the vertebrates, offer the strongest 



