CIRCULATORY APPARATUS OF THE NEMERTEA, 69 
SuMMARY. 
We have seen that there are three types of vascular system 
in the Nemertea. Though the families of the Valenci- 
niidz and the Poliide belong to the Paleonemertea, 
they, with respect to their vascular and nephridial system, 
already approach the Schizonemertea. To avoid con- 
fusion, I will here employ the expressions, ‘ Paleo-type,”’ 
““ Schizo-type,” and “ Hoplo-type.”’ 
In the Palzo-type we have two longitudinal blood-spaces, 
which communicate forwards in the head above the probos- 
cidian sheath, are lacunar in the head and the- cesophageal 
region. They have in the cesophageal region a tendency to 
enlarge their surface, but are true vessels in the intestinal region, 
and communicate in the tail above the intestine. 
In the head also, lacunar communications may occur beneath 
the proboscidian sheath. In the cesophageal region the surface 
is enlarged, owing either to the fact that the lacune are large 
(Cephalotrix), or that portions are constantly being detached, 
which, however, remain in open connection with the principal 
lacune (Carinella), or that along the whole csophageal 
region the lacunez have divided into two stems, which only in 
the foremost part permanently communicate (Carinoma). 
The vessels in the tail of Carinella open directly into one 
another, thus forming a loop above the intestine. In Cari- 
noma lacunar spaces communicate above the proctodeum, 
representing rudimentary transverse vessels. 
Moreover, in some forms of the Palzo-type (Carinella, 
second form of Carinoma) two other vessels occur in the weso- 
phageal region and in the proboscidian sheath. Their con- 
nection with the vascular system could only be demonstrated 
with certainty in exceptional cases. 
In the Schizo-type we find: in the head, lacunar spaces 
which communicate both above and beneath the proboscidian 
sheath; in the esophageal region also, lacunar spaces which 
coalesce round the @sophagus on the ventral side. Two lacune 
on the sides of the proboscidian sheath are more permanently 
