4 A. ©. OUDEMANS. 
the median dorsal vessel into the proboscidian chamber (the 
cavities, however, remaining separate) in the cesophageal 
region, without, however, following up the further course of this 
vessel anteriorly. 
The description which Barrors (29) gives of the blood-ves- 
sels of the Nemertea is eminently fantastic and in no respect 
borne out by direct observation of sections. He denies the 
presence of transverse vessels in the unarmed species (although 
DELLE CuHIasE, BLANCHARD, KerersteIn, McInrosn, and 
Husrecut vouch for them!), and looks upon the genital sacs 
as establishing a direct and metamerically arranged communi- 
cation between the longitudinal vessels ; these sacs thus form- 
ing part of the circulatory apparatus! He, moreover, mentions 
a posterior communication between the proboscidian sheath 
and the median blood-vessel. I would venture to suggest that 
it is the more or less complicated lacunar arrangement in 
the esophageal region that has led astray in this respect so 
conscientious and accurate a naturalist. 
The circulatory apparatus of Malacobdella has been in- 
vestigated by Buancuarp (6), Szmper (28), Horrmann (80), 
and Von Kennex (81). The latter furnishing by far the 
most accurate description. 
GrarF (37), GuLLIvER (36), and Dewoterzky (38), have not 
materially added to our knowledge of the circulatory apparatus. 
With respect to the nephridia this historical introduction 
can be very concise. It is the merit of Von Kennex (81) 
to have correctly traced this system in different species, 
and to have given most satisfactory histological descriptions 
of it. 
There is reason to suppose, however, that already DELLE 
CuiasE (1, 2) was aware of its existence, and actually observed 
it in one of his species (Descrizione, p. 128, vol. iii). It has 
since been noticed by Max Scuutrze (11, 12), and more 
reservedly been referred to by Husrecut (19). 
McInrosu (18) denies its existence, and suggests that Max 
ScHuLtzE has confounded the circulatory with the excretory 
apparatus. 
