well-differentiated stomach in the manner of a saddle. The stomach itself, as in chelonians generally, has a markedly transverse position and passes under cover of the right lobe of the liver into the duodenum. The coils of small intestine form a prominent mass, which, however, when unravelled as shown in the figure, permits us to recognize its identity with the mammalian embryonic umbilical loop. The well-marked ileo-colic junction is situated at the termination of the returning limb of the loop, close to the beginning of the descending limb. This close approximation of the duodenum and colon (duodeno-colic isthmus) forms one of the most important factors in the further development of the mammalian intestinal canal and will again be referred to below. [Illustration: FIG. 105.--_Rana catesbiana_, bull-frog. Alimentary canal and appendages. (Columbia University Museum, No. 1454.)] [Illustration: FIG. 106.--_Pseudemys elegans_, pond turtle. Alimentary canal. (Columbia University Museum, No. 1437.)] From the ileo-colic junction the large intestine of the turtle continues caudad to the cloaca in a nearly straight line. The same primitive condition of the intestinal canal may be observed in some members of man's own class, the mammalia--as in certain edentates. Figs. 107 and 108 show the entire abdominal portion of the alimentary tract in _Tamandua bivittata_, the little ant-eater of Brazil. The stomach is turned cephalad and the great omentum elevated. The intestines are turned over to the right side. [Illustration: FIG. 107.--Abdominal viscera of _Tamandua bivittata_, the little ant-eater, seen from the left, with the intestines turned to the right. (From a fresh dissection.)] [Illustration: FIG. 108.--The same view, from another specimen. Figures 107 and 108 should be studied and compared together, as each supplements the other.] It will be observed that in spite of the numerous coils of the small intestine the general arrangement of the alimentary canal corresponds to the primitive scheme shown in Fig. 98. The entire intestinal canal is attached by a continuous vertical mesentery to the dorsal median line of the abdominal cavity ventrad of the vertebral column and aorta. The growth in length of the small intestine has necessitated a corresponding lengthening of the attached border of the mesentery--consequently the membrane presents a pleated or crenated appearance. The caecum is well developed, the ileo-caecal junction being situated within the returning limb of the loop, a little distance from the apex.