126 



GENERAL PRINCIPLES OF ZOOLOGY, 



Various Divisions and Appendages of the Digestive 

 Tract. The part which the archenteron takes in com- 

 parison with the ectodermal proctodoeum and stomodoeum 

 in making up the completed digestive tract is very differ- 



FIG. 56. 



FIG. 57. 



FIG. 56 Bee-larva just after hatching : seen from the ventral surface. The digestive tract 

 consists of three portions: a, fore-gut ; >, mid-gut ; e, hind-gut mot yet connected with the 

 mid-gut);.^, limits of segments; st, stigma; t, trachea; , ventral nerve-cord. (After 

 Butschli). 



FIG. 57. Digestive tract of the domestic fowl, a, oesophagus ; t>, crop ; <-, glandular 

 stomach ; </, gizzard ; e, liver ; _/", gall-bladder ; g; pancreas; /, z, small intestine ; k, 

 cceca ; /, large intestine ; >, ureters ; , oviduct ; a, cloaca. 



ent in the various animal groups. On one side the insects* 

 on the other side the vertebrates, offer the strongest con- 

 trast ; the insects have a very short mid-gut and conse- 

 quently a long extent of fore- and hind-gut formed from 



