384 EMBRYOLOGY OF THE LOWER VERTEBRATES oh. 



of the development of the Bird's heart are those of Greil, of which 

 unfortunately there is available so far only the abstract given by 

 Hochstetter (1906). As we should expect from the close genetic 

 relationship between Birds and Reptiles there is a close correspond- 

 ence between the general features of the development of the heart 

 in the two cases. It will suffice then to draw attention to the more 

 important points in which the development of the Fowl's heart has 



Pio. 182. — Illustrating the development of the heart in the fowl. 

 (After original drawings by Greil.) 



at, atrium ; b.a.f, bulbo-auricular fold ; c, conus ; La, left auricle ; l.i, left innominate artery ; l.p, 

 left pulmonary; l.V, left ventricle; r.a, right auricle; r.i, right innominate artery; r.p, right 

 pulmonary ; r.V, right ventricle ; s.A, systemic aorta. 



been found to differ from that of Lacerta. So far as external form is 

 concerned the most striking difference is that the sinus venosus 

 loses its identity as a distinct chamber of the heart. It becomes as 

 it were incorporated in the right auricle, all except its left portion 

 which persists as the cardiac end of the left duct of Cuvier or 

 anterior Vena Cava. 



An important advance upon the condition in Lacerta is found in 

 the division of the ventricular part of the heart into a right and a 



