Ill 



LUNG- 



171 



the archaic mode of development, the lung-rudiment (Fig. 9*7, I) 

 describes a spiral curve round the oesophagus so that the bifurcated 



Fig. 97. — Portions of ■ transverse sections through a Lepidosiren larva (stage 34) to 

 illustrate the changing relations of lung to gut from a short distance behind the glottis 

 tailwards. In A the lung is ventral to the alimentary canal ; in B it is directly to the 

 right ; in C it has become displaced dorsally ; while in D (where it is commencing to 

 bifurcate) it has come to be mid-dorsal in position. 



A, aorta; gl, glomerulus of pronephros ; I, lung; N, notochord; oes, oesophagus. 



hinder end of the rudiment, which will give rise to the lungs in the 

 restricted sense, comes to he dorsal to the alimentary canal. 



The lungs continue their tailward growth in the substance of the 



