Ill 



LUNG 



171 



the archaic mode of development, the lung-rudiment (Fig. 97, /) 

 describes a spiral curve round the oesophagus so that the bifurcated 



hnbtiil 



- - oes. 



linililiil 





liiiiliinl 



FIG. 97. Portions of transverse sections through a Lepidosireu larva (stage 34) to 

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

 tail wards. 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 

 1>ii'mrate) it has come to be mid-dorsal in position. 



A, aorti ; ijJ, gloinerulus of pronophros ; I, lung; N, notochord ; oes, oesoplia.mis. 



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

 restricted sense, comes to lie dorsal to the alimentary canal. - 



The lungs continue their tailward growth in the substance of the 



