539 



thoracic region of a 14 mm cat embryo, it is seen that the position 

 occupied by the thoracic and right lymphatic ducts in the 16 mm em- 

 bryo (Fig. 7) is identically the same as that assumed in the 14 mm 

 embryo (Figs. 8 and 9) by the outgrowths from the ventral surface of 



Right azygos 



Left az_ygos 



fjf^y 



Anlage of 

 R. lymph, duet 



Aort;i 



Fig. 9. 



Anlage of 

 Thoracic duct 



Figs. 8 and 9. Microphotographs of two successive transverse sections taken 

 through the body of a 14 mm cat embryo in the region of the thorax which show the 

 origin of the veno-lymphatic anlages of the thoracic and right lymphatic ducts as out- 

 growths from the ventral surface of the azygos veins. 



