48 A. ©. OUDEMANS. 
even with a glass of magnifying power of 30—40 times, having 
been better coloured (picro-carmine of Ranvier). 
In neither of the two specimens were the excretory ducts 
open. They were sometimes filled by a granular secretion, so 
that I could not observe the cilia. Here I did not see any 
difference between the foremost and hindmost ducts. On 
observing the two lists one is inclined to conclude that 
they arise here irregularly, though always segmentally projected 
in pairs. 
7. Lineus gesserensis (O. F. M.), McInt. 
Similar to the foregoing species, but the two proboscidian 
sheath lacune, even in the foremost part of the cesophageal 
region, are not so well separated by transverse bands from the 
remaining lacune. 
The specimen, owing to the insufficient preservation of the 
microscopical slices, was not suitable for closer examination of 
the nephridial system. 
8. Cerebratulus marginatus (Ren.), fig. 65. 
In the main resembling Lineus sanguineus. 
The lacune, which go downwards to communicate with the 
dorsal vessel, first form a true vessel, which only a few sections 
further backwards penetrates the wall of the proboscidian 
sheath. More than elsewhere this vessel displays a different 
character in its upper and lower arch. The cells of the upper 
side are stretched, are situated against each other, and are 
fan-shaped in their arrangement. Next to the proboscidian 
sheath in the brain region lie two large lacune, separated from 
those that embrace the mouth by a horizontal transverse band 
of muscular fibres, as in Lineus. In these large lacune the 
posterior brain lobes bathe, which extend far backwards, even 
behind the slit of the mouth. 
In another fragment, which belonged to the cesophageal 
region, but was situated further backwards, I saw, next to the 
proboscidian sheath, in the angle formed by its wall and the 
longitudinal muscular coat on both sides, a longitudinal vessel, 
