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 
vessel, and probably 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 cavity (fig. 20, cnt.) 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 "tonoue 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, 
vgs.) 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 my preparations show a distinct capillary net 
in the gill septa, in some I have observed small branches passing 
from the septal vessel, and these probably represent part of the 
capillary net Spengel has found so richly developed in the gill 
septa of Pt. sarniensis. 
