38 
ON A NEW SPECIES OF ENTEROPNEUSTA, 
limiting membrane of the collar cord to form the capillary net on 
on its dorsal surface, and branches also pass downwards in the 
boundary membrane laterally to the perihpemal spaces and come 
into direct connection with the capillary net of the inner wall of 
the collar. Very few vessels leave the ventral side of the dorsal 
vessel in this species, and the capillary net of the inner wall of 
the collar thus appears to stand mainly in connection with vessels 
derived from the dorsal side of the dorsal vessel, in common with 
the capillary net of the collar cord. 
Ventral Vessel of Trunk : The ventral vessel is related exactly 
as in Pt. minuta. It does not extend so far posteriorly as the 
dorsal, but disappears at the point of origin of the keel-shaped 
process of the gut. 
Lateral Vessels : The lateral vessels are essentially similar to 
those of the described species. In the branchial region they 
occupy the usual position just below the submedian lines (fig. 20,, 
lh\). Then when the lateral septa appear, they run in these (fig. 
22, llv.). Towards the ends of the septa the vessels gradually 
pass downwards towards the point of attachment of the septa to 
the gut, and then behind the termination of the septa they con- 
tinue as free vessels lying in the interior of the now greatly 
reduced genital wings (fig. 24, llv.) and which finally about the 
middle of the hepatic region pass over into the gut capillaries. 
In this part of their course the vessels possess, as in the other 
species, circular muscle fibres in their Avails, and also from the 
latter there radiate outwards fine fibres (fig. 24, llv.), probably 
functioning as expansors. 
Gill Vessels : My observations on this very complicated set of 
vessels confirm, so far as they go, those of Spengel. The afferent 
gill vessels arising from the dorsal vessel vary according as the 
dorsal vessel occupies the whole of the mesentery or only its 
dorsal half. In the former case the afferent vessels pass off 
directly from the ventral side of the dorsal vessel; in the latter 
they diverge outwards and downwards from its ventral side, the 
mesentery being apparently absent at this point. The afferent 
