DISTRIBUTION OF SUBCUTANEOUS VESSELS IN GANOIDS 125 



Strange to say, in Poly o don a great mass of lymphoid tissue 

 surrounds the heart, which is supplied by the coronary blood 

 vessels, and from which a lymphatic network arises that evidently 

 reaches the veins through the medium of the oesophagus plexus. 



Only in the caudal region of Polyodon were dorsal and ven- 

 tral trunks found. They were present and extremely large in 

 the thoracic region of Leptsosteus ; while in Polyodon all of the 

 subcutaneous vessels of the trunk were very minute. 



