392 



Habriet Lehmanh. 



books and papers, but since they are valuable for comparison in this 

 connection, they are reproduced in Text-Fig. F. Rathke's investigations 

 cleared many misconceptions, and subsequent observations have shown 

 them to be in the main, accurate. 



Lizard 



Snake 



Bird 



Mammal 



Fig F. 



Eathke's diagrams, published 1857, showing transformation of the aortic arches 



in the lizard, snake, bird and mammal. 



Sabatiee (1874) differs from Rathke in ascribing the origin of the 

 subclavian in birds and the crocodile to the dorsal end of the third arch. 

 Bus diagrams (shown in Text-Fig. G), therefore correspond in this respect 

 to those of VON Baer and Thompson for birds and mammals. Sabatier's 

 conception of the formation of the subclavian in birds necessitates a com- 

 plete disappearance of the left fourth arch and the left aortic root, as 

 shown in Text-Fig. G. 



The earlier papers of Bo AS (1881, 1882) showed the presence of a 

 fifth arch in the Dipnoi, and larvae of certain Amphibia, and were im- 

 portant later in supplying the basis for his conclusions in regard to the 

 number of aortic arches in the higher vertebrates. (See further under the 

 year 1887.) 



