110 DR. THOMAS ALCOCK ON THE 



70. A tadpole taken from the pond had a piece of intestine 

 about half an inch long hanging from a small perforation 

 in the wall of the abdomen near the vent. On cutting 

 awav the skin from the ventral surface, the whole of the 

 great coil of intestine was found to be absent, none of the 

 alimentary canal remaining except the short length which 

 hung externally and a loop in close connexion with the 

 liver. The left lung was seen filled with air ; and its free 

 end floated up in the water in which the tadpole was ex- 

 amined. When the liver was removed the right lung was 

 also brought into view. An enlarged drawing was made, 

 showing the heart, gills, and lungs. 



72. A fine tadpole with the hind legs well developed 

 and carried in a frog-like manner was taken; and a 

 drawing was made, of the natural size. On examining 

 the abdominal viscera the intestine was found almost 

 empty. 



72 (2). By removing the liver and intestine the lungs 

 were exposed. They were of equal size, long, narrow, and 

 tapering to a blunt point. A drawing was made of one of 

 them under the microscope with the two-inch object-glass. 

 It consisted of a sacculated tube composed of structureless 

 membrane in which small pigment- cells were scattered. 



Some pieces of meat were put into the pond to supply 

 the tadpoles with food. 



73. Crowds of tadpoles were eagerly feeding on the 

 meat. Two were selected, one in an advanced stage of 

 development, the other more backward. Enlarged draw- 

 ings of the left side of each were made, showing the open- 

 ing of the gill-chamber at the end of a short, projecting, 

 conical tube, and also the remarkable change in the shape 

 of the body as development advances. 



73 (2) . A drawing was made of the lungs of the larger 

 of the two tadpoles. 



