CIROULATORY APPARATUS OF THE NEMERTEA. 35 
but in none of my preparations did I see circular fibres sur- 
rounding them, only a thin hyaline basal layer, and occasionally 
epithelium. They stuck, as it were, to the diverticula; their 
wall, at the same time, was the wall of the intestine. 
In the hindmost half of the intestinal region the lacunar 
spaces of the sides of the proboscidian sheath are absent. They 
have gradually disappeared (fig. 15), and now only three longi- 
tudinal vessels occur (figs. 16,41) with their transverse vessels, 
which are visible down to the hindmost communication of the 
three longitudinal vessels above the proctodeum; sometimes 
this latter communication is invisible. 
The lacune surrounding the esophagus and the two long 
lacunar spaces next to the proboscidian sheath in the foremost 
half of the intestinal region are always internally limited by 
the epithelium cells already mentioned; externally by an 
extremely thin hyaline basal layer. In the dorsal vessel, as soon 
as it lies beneath the proboscidian sheath outside the hyaline 
basal layer, a thick layer of circular muscular fibres are seen ; 
also in the two ventral vessels. In vain did I look for longi- 
tudinal fibres. The two ventral vessels lay in a fold, turned in- 
wards, of the intestine amidst a gelatinous stroma that filled up 
this fold. This stroma has a radiating arrangement round the 
vessel. Probably these rays are local thickenings arising from 
the violent contraction of the vessel. In the stroma great 
granular nuclei were visible. The whole looked almost like 
fig. 63. 
Let us now, with respect to the vascular system, compare 
Valencinia with Carinoma and Carinella. We have seen 
that Carinoma in its head (except in the arrangement of the 
lacune) greatly resembles Valencinia, and that the remain- 
ing body bears a likeness to that of Carinella, with some 
differences in the csophageal region and in the nephridial 
system. Both in Carinoma and Carinella there is an @so- 
phageal region which differs from the rest of the body by the 
blood-spaces in this region having here a strong tendency to 
detach from themselves portions (Carinella), or have even 
already finished this process (Carinoma), especially Cari- 
