BY JAS. P. HILL. 39 



vessels arise from the dorsal vessel opposite the gill tongues. Each, 

 according to Spengel, divides soon after its origin into two vessels 

 — one of which passes into the tongue and divides again to form 

 the two vessels running along the tongue prongs, the other passes 

 to the gill septum in front of the tongue which received the first 

 A'essel, and probal^l}^ becomes continuous with the septal vessel. I 

 have not been able to make out from my preparations the above 

 described connections to my complete satisfaction. Each of the 

 afferent vessels seems to stand in connection with a vessel lying- 

 just above the line of attachment of the gill tongue, and this 

 vessel extends on to the dorsal edge of the succeeding septum, and 

 is situated just above the dorsal end of the gill skeleton. Through 

 this vessel there is doubtless established the connection between 

 the blood flowing in the gill tongues and that in the septa. 



The vessels in the tongue are exactly as described by Spengel. 

 In transverse sections through the branchial region the capillary 

 net in the tongue situated immediately below the peritoneal 

 covering of the tongue cavit}" (fig. 20, C7it.) can be distinctly seen, 

 and especially in horizontal sections the larger vessels of the net, 

 viz., the large vessel situated immediately under the epithelium of 

 the "tongue back" and the two smaller vessels along the inner 

 side of each tongue prong (fig. 21, tp.) can be distinctly recognised 

 (fig. 21). In each of the gill septa the septal vessels (figs. 20, 21, 

 tigs.) can readily be made out running just external to the septal 

 prong (spr.). At their ventral ends the septal vessels stand in 

 connection with the "limiting vessel" below the boundary cushion 

 between the branchial canal and the oesophagus, and this "limit- 

 ing vessel" stands in the usual connection with the capillary net 

 on the wall of the oesophagus. 



Though none of m}'- preparations show a distinct capillar}'- net 

 in the gill septa, in some I have observed small branches jDassing 

 from the septal vessel, and these probal^ly represent part of the 

 capillary net Spengel has found so richly developed in the gill 

 septa of Pt. saymiensis. 



