ALIMENTARY SYSTEM. 501 
From the hindmost region of the gut, the allantois 
grows out in all animals from Amphibians onwards. In 
Amphibians it is represented by a cloacal bladder ; in the 
higher Vertebrates it is a vascular foetal membrane con- 
cerned with the respiration or nutrition of the i or 
both, 
Fic. 267. Beri through a young newt. 
c.2,, Connective tissue ; Z., epidermis; D., dermis; S.C. spinal cord; J7., 
muscle; JV., notochord Sh, mesodermic sheath of notochord; K., 
kidney; 2, lung; S 5 spleen 3 3 ST., stomach; Pe., peritoneum 3 L., 
liver; a@., duct of the pancreas (P); G.B., gall-bladder ; Bex dorsal 
aorta. . 
Cilia are very common on the lining of the intestine in 
Invertebrates, but.they are much rarer in Vertebrates. Yet 
as they occur in Amphioxus, lampreys, many fishes, Proto- 
pterus, some Amphibians, and in embryonic Mammals, it 
