9 A. CG. OUDEMANS. 
description of his Polia siphunculus (=Cerebratulus 
marginatus, Ren.) he describes it as follows : 
“Dalla fine della bocca principia una piccolissima vena, che 
sull’ intestino manda un vasellino ad ogni sua borsa laterale”’ 
(1. p. 434). 
His figure (Tav. xxviii, fig. 3) very clearly shows both the 
dorsal vessel and the smaller transverse vessels situated one 
above each diverticulum of the intestine. 
‘Ducks (3) is the next to mention blood-vessels in the dif- 
ferent species of his genus Prostoma (=Tetrastemma). 
He mentions one median and four (!) lateral longitudinal 
vessels, two on each side, communicating with each other in 
the head. 
Jounston (4) erroneously regarded the brain as a double 
heart, the longitudinal nerve-stems as vessels. Several later 
authors have fallen into the same error. 
RatuHKeE (5) carefully avoided it and describes the median 
and the two lateral longitudinal vessels of Lineus. 
QuaTREFAGES (7) in his splendid treatise on this group of 
worms has given an accurate description of the circulatory 
system of certain Hoplonemertea. He, however, too 
peremptorily looked upon this description as applying 
to all Nemertea, whereas most considerable differences 
obtain in the other groups. However, his figures have 
found their way into most of the text-books of zoology as 
correctly illustrating the vascular system of the Nemertea 
indiscriminately. 
His colleague Brancuarp (6, 8, 9, 10) minutely describes 
injections made by him of the Nemertean vascular system as 
well as their results. It is hardly probable that he indeed suc- 
ceeded in injecting the true blood-vessels ; on the contrary, it 
may be fairly inferred that it was the proboscidian sheath 
which he operated upon. 
The results with respect to the Nemertean vascular sys- 
tem to which Max Scuutrze (11, 12), Kererstetn (14), 
vaN Brnepen (13), and Cuaparepe (15) have been led 
by their respective researches, have been carefully recorded 
