Subcutaneous Vessels in Tail of Lepisosteus 73 



were not connected, and which drained their respective halves of the 

 arches. Those from the ventral portion of the arch emptied into the 

 inferior jugular, while those from the dorsal portion terminated in 

 dorsal branchial sinuses, Avhich were in communication with the sub- 

 cutaneous system and with the jugular through the cephalic sinns. 

 Similar dorsal branchial lymphatic sinuses were described in Scor- 

 pcenichthys as being in communication with the subcutaneous system 

 and with the jugular through the cephalic sinus. No branchial lym- 

 phatic trunks were seen emptying into them, but both dorsal and 

 ventral nutrient branchial veins were shown uniting directly with the 

 jugular and the inferior jugular veins. It would seem that the only 

 explanation of the above complicated condition of affairs is that a part 

 of the subcutaneous system found in the region of the gills has become 

 entirely separated and has reverted back to veins in the higher orders 

 of fishes. 



In the Teleosts there is a further differentiation or rather addition. 

 Here we find that the rudimentary haemal trunk in the hsemal canal of 

 the Selachians and Ganoids has developed into a conspicuous trunk 

 with numerous hsmal branches that communicate ventrad' with the 

 ventral trunk. There is also in Scorpceniclithys and in many Teleosts 

 a large and important neural longitudinal trunk, which traverses the 

 neural canal above the spinal cord and sends off numerous anastomosing 

 branches to the dorsal trunk. 



In conclusion it may be said that considerable anatomical data sup- 

 port the hypothesis that the subcutaneous vessels of the Teleosts and 

 Batrachians, which are evidently lymphatics, have their homologue in 

 the somewhat similar system of the Selachians, which has much the 

 ap^warance of veins. The subcutaneous system of the Ganoids is appar- 

 ently a sort of intermediary ; that of Poljjodon. one of the cartilaginous 

 Ganoids, resembling the arrangement of the Selachians, and that of 

 Lepisosteus, one of the bony Ganoids, approaching the system of the 

 Teleosts and Batrachians. 



LIST OF ABBREVIATIONS USED IN THE FIGURES. 

 A. or P. prefixed to an abbreviation signifies anterior or posterior ; R. or L., 

 right or left ; a series is numbered from cephalad to caudad. 

 A. R., anal fin rays. 



A. R. C, anal ray subcutaneous canals. 

 A. R. M., anal ray levator and depressor muscles. 

 C, in Fig. 10, communication between the lateral and haemal trunks. 



